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Photonics West 2011: Presentations on femtosecond lasers and applications

Femtosecond laser-induced formation of AuAg nanoalloys from aqueous mixture of metallic ions

Paper 7922-8 of Conference 7922
Date: Monday, 24 January 2011
Time: 11:40 AM – 12:00 PM

Author(s): Yuliati Herbani, Takahiro Nakamura, Shunichi Sato, Tohoku Univ. (Japan)
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The synthesis of AuAg alloy nanoparticles of various compositions has been performed for the first time by femtosecond laser irradiation of the aqueous mixture solution of metallic ions. The mixture of silver-ammonia complex and chloroaurate ions was simply introduced into a glass vial and exposed for several minutes to tightly focused femtosecond laser pulses which induced a strong optical breakdown in the solution and promoted the formation of hydrogen radicals and the solvated electrons to reduce the metallic ions. Homogeneous AuAg nanoalloys have been produced and no oxidation of Ag particles has been observed.

Identification of extremely radiative nature of AlN by time-resolved photoluminescence and time-resolved cathodoluminescence measurements

Paper 7937-34 of Conference 7937
Date: Monday, 24 January 2011
Time: 4:05 PM – 4:30 PM

Author(s): Shigefusa F. Chichibu, Kouji Hazu, Takeyoshi Onuma, Tohoku Univ. (Japan); Takayuki Sota, Waseda Univ. (Japan); Akira Uedono, Univ. of Tsukuba (Japan)
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(Invited) AlN is one of the promising candidates for the realization of light emitters workable in far ultraviolet wavelengths. To know the material talent, quantitative understanding on the radiative lifetime for the near-band-edge mission is essential. However, there have been few reported results on the time-resolved photoluminescence (TRPL) measurement on AlN. In this presentation, radiative lifetimes for the near-band-edge emission in AlN epilayers of various crystal qualities obtained using TRPL and time-resolved cathodoluminescence measurements will be correlated with the point defect concentration probed by the positron annihilation measurement, in order to discuss the impacts of growth parameters on the lifetimes.

High-throughput in-vivo vertebrate imaging and screening (Keynote Presentation)

Paper 7902-9 of Conference 7902
Date: Saturday, 22 January 2011
Time: 1:55 PM – 2:15 PM

Author(s): Mehmet F. Yanik, Carlos Pardo, Tsung-Yao Chang, Bryan Koo, Cody Gilleland, Steven Wasserman V.D.M., Massachusetts Institute of Technology (United States)
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We demonstrate the first high-throughput platform for cellular-resolution in vivo pharmaceutical and genetic screens on vertebrates (Nature Methods, August 2010). The system automatically loads zebrafish from multiwell plates, and positions and orients them for high-speed multifocal confocal imaging and ultrafast laser manipulation of both superficial and deep organs within 19sec without damage. We show screening of retinal axon guidance mutants and neuronal regeneration assays in combination with femtosecond laser microsurgery. Our technology can permit large-scale in vivo drug screens on organ development, neural degeneration/regeneration, stem cell proliferation, cardiovascular, immune, and endocrine systems, pathogenesis, cancer, and toxicity of drugs on vertebrates.

OCT-guided femtosecond laser system for cataract surgery

Paper 7885-23 of Conference 7885
Date: Saturday, 22 January 2011
Time: 4:45 PM – 5:00 PM

Author(s): Daniel V. Palanker, Stanford Univ. School of Medicine (United States); Georg Schuele, OptiMedica Corp. (United States); Neil Friedman, Stanford Univ. School of Medicine (United States); Dan E. Andersen, OptiMedica Corp. (United States); Mark S. Blumenkranz, Stanford Univ. School of Medicine (United States); Juan Batlle, Rafael Feliz, Centro Láser (Dominican Republic); Jonathan H. Talamo, Harvard Medical School (United States); George R. Marcellino, OptiMedica Corp. (United States); Barry Seibel, Seibel Vision Surgery (United States); William Culbertson, Bascom Palmer Eye Institute (United States)
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OCT-guided fs laser system has been developed to improve precision and reproducibility of cataract surgery. Capsular strength after laser capsulotomy was nearly twice stronger than after manual capsulorhexis: 124mN vs. 66mN. Average deviation from intended size in laser capsulotomy was eight times better than with capsulorhexis: 32ตm vs. 240ตm. Roundness of laser capsulotomy improved by a factor of six compared to manual procedure: deviation of 1.5% vs. 10%. This system greatly enhances exactitude in centration of IOLs. Lens segmentation facilitates its splitting into quadrants and nucleus fragmentation speeds up its emulsification. Multi-planar corneal incisions provide for self-sealing wound constructions.

Lowering threshold energy for femtosecond laser pulse photodisruption through turbid media using adaptive optics

Paper 7885-25 of Conference 7885
Date: Saturday, 22 January 2011
Time: 5:15 PM – 5:30 PM

Author(s): Anja Hansen, Tammo Ripken, Laser Zentrum Hannover e.V. (Germany); Ronald R. Krueger, The Cleveland Clinic (United States); Holger Lubatschowski, Laser Zentrum Hannover e.V. (Germany)
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For femtosecond laser pulse applications in the posterior eye aberrations cause a distortion of the wavefront and therefore an increased focal volume which reduces the photon density and thus raises the threshold energy. The influence of adaptive optics on lowering the threshold energy by refining a distorted focus was investigated. The adaptive optics system can correct for aberrations introduced by a turbid object with low optical quality. The effects of the laser pulses on a retina model were examined microscopically and compared for the aberration corrected and uncorrected case. A threshold energy reduction is possible when using adaptive optics.

Microfluidic manipulations with sub-cellular optical resolution

Paper 7943-2 of Conference 7943
Date: Sunday, 23 January 2011
Time: 11:00 AM – 11:30 AM

Author(s): Mehmet F. Yanik, Massachusetts Institute of Technology (United States)
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We present microfluidic and ultrafast optical technologies for studying complex physiological processes in vivo such as neuronal regeneration and degeneration, and stem cell proliferation in both invertebrate and vertebrate animal models. These technologies include microfluidic whole-animal manipulators, as well as integrated chips containing multiple addressable incubation chambers for exposure of individual animals to compounds and for sub-cellular time-lapse imaging of hundreds of animals on single chips. Using femtosecond laser nanosurgery, we performed the first in vivo screen for compounds enhancing neuronal regrowth. We discovered highly potent compounds with a wide variety of cellular targets that enhance neuronal regeneration.

Elucidating optimal photodisruption parameters in the femtosecond laser nanoablation of cellular membranes

Paper 7925-9 of Conference 7925
Date: Sunday, 23 January 2011
Time: 1:20 PM – 1:40 PM

Author(s): Daniel S. Eversole, Sigfried Haering, Adela Ben-Yakar, The Univ. of Texas at Austin (United States)
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Plasmonic Laser Nanosurgery (PLN) is a novel technique that relies on the large enhancement of femtosecond laser pulses in the vicinity of gold nanoparticles to photodisrupt nanoscale-structures in live cells. Surface plasmon excitation in gold nanoparticles provides a platform for the confinement of photoactivated-processes, while targeting methods provide the highest level of therapeutic selectivity. We studied optoporation efficiency of PLN for MDA-MB-468 and NIH-3T3 cell lines utilizing 10 kDa FITC-Dextran influx and calcein red-orange viability staining. We will present the effects of irradiation duration, particle labeling, and laser polarization on optoporation efficiency. We will also present three-dimensional photodisruption and transfection.

High-power femtosecond hybrid Ti:sapphire: KrF laser facility and its applications

Paper 7915-12 of Conference 7915
Date: Sunday, 23 January 2011
Time: 2:30 PM – 2:50 PM

Author(s): Andrey A. Ionin, Sergej I. Kudryashov, Alexey O. Levchenko, Leonid V. Seleznev, Dmitry V. Sinitsyn, Nikolay N. Ustinovskii, Vladimir D. Zvorykin, P.N. Lebedev Physical Institute (Russian Federation)
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High-power hybrid femtosecond laser facility consisted of a front-end Ti:Sapphire laser system emitting the third harmonic radiation at the wavelength 248 nm and a set of excimer KrF laser amplifiers is now under development at the Lebedev Institute. Peak power comes up to a few TW right now. Recent experiments on applications of high-intensity femtosecond pulses with wavelengths 248nm and 744 nm for multiphoton and tunnel ionization of different gases, formation of mini-filaments in air under the tight focusing, and laser surface nanostructuring of various solid materials such as titanium, silicon, etc., are discussed.

Optoporation and transfection of cells with kHz and MHz repetition rate femtosecond lasers

Paper 7925-13 of Conference 7925
Date: Sunday, 23 January 2011
Time: 2:40 PM – 3:00 PM

Author(s): Andrew A. Davis, Matthew J. Farrar, Nozomi Nishimura, Moonsoo Jin, Christopher B. Schaffer, Cornell Univ. (United States)
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We quantified the formation and resealing of transient pores formed in cell membranes by irradiation with femtosecond laser pulses and correlated hole mechanics with cell viability and expression of DNA plasmids introduced through the hole. We also compared optoporation parameters between a low repetition rate regenerative amplifier (1 kHz) and a high repetition rate oscillator (76 MHz). Our results indicated that hole size determined the probability of acute hole resealing, which in turn predicted long-term cell viability, that hole radii increased with laser energy, and that cells could be reliably transfected with appropriate parameters using either laser system.

Autocorrelation of femtosecond VUV pulses using multiphoton ionization

Paper 7915-15 of Conference 7915
Date: Sunday, 23 January 2011
Time: 4:00 PM – 4:20 PM

Author(s): Shoichi Kubodera, Wataru Nagaya, Hironari Zushi, Masanori Kaku, Masahito Katto, Univ. of Miyazaki (Japan)
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We have been developing a simple and versatile autocorrelator utilizing multiphoton ionization of gaseous media to characterize femtosecond laser pulses, which could be used in the wide wavelength regions between infrared (IR) and vacuum ultraviolet (VUV). Femtosecond IR laser pulses were characterized by autocorrelated electron signals of rare gases. Although Xe should have required nine photons to be ionized with the IR laser at 882 nm, the four-photon ionization was observed. By using the fourth-order correlation function, the pulse width of 173 fs was determined for the 882 nm laser, which agreed with that measured with a two-photon autocorrelator.

Optoacoustic response of a single submicronic gold particle revealed by the picosecond ultrasonics technique

Paper 7937-15 of Conference 7937
Date: Sunday, 23 January 2011
Time: 4:00 PM – 4:25 PM

Author(s): Yannick Guillet, Clément Rossignol, Bertrand Audoin, Mélanie Ferrie, Serge Ravaine, Univ. Bordeaux 1 (France)
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A growing interest is shown in characterizing elastic properties of the matter at submicron scale. A promising way to probe elasticity at a nanometer scale is to consider a single nanoparticle as an opto-acoustic nanotransducer. Since the late 90's, pump-probe experiments have revealed as a powerful way to investigate elastic properties of nanoparticles. We report here on pump-probe transient reflectivity measurements which reveal a new detection mechanism of elastic vibrations of a single submicron gold particle. We then demonstrate the detection of the sound propagation in an agar gel matrix (a biological phantom), through the enhancement of the Brillouin scattering.

Nanoparticle mediated femtosecond laser photodisruption mechanisms

Paper 7925-16 of Conference 7925
Date: Sunday, 23 January 2011
Time: 4:10 PM – 4:30 PM

Author(s): Sigfried Haering, Richard K. Harrison, Adela Ben-Yakar, The Univ. of Texas at Austin (United States)
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Due to the increased absorption and near-field enhancement of plasmonic nanoparticles, exceptionally energy efficient photodisruption mechanisms may be excited when coupled with femtosecond laser pulses. To understand, predict, and apply such methods to phototherapy, we have both experimentally measured bubble formation around 50 nm gold spheres exposed to NIR femtosecond pulses and assembled a comprehensive photodisruption model including particle enhancement, heating, and ablation theories.

Plasmonic enhanced femtosecond-laser optoporation and transfection of human melanoma cells

Paper 7925-17 of Conference 7925
Date: Sunday, 23 January 2011
Time: 4:30 PM – 4:50 PM

Author(s): Judith Baumgart, Ecole Polytechnique de Montréal (Canada); Laure Humbert, Royal Victoria Hospital (Canada); Bastien St.-Louis Lalonde, Ecole Polytechnique de Montréal (Canada); Jean-Jaques Lebrun, Royal Victoria Hospital (Canada); Michel Meunier, Ecole Polytechnique de Montréal (Canada)
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Melanoma is a complex and aggressive cancer and over the past 50 years, its incidence in most developed countries has increased faster than any other cancer. We have investigated the use of a femtosecond (fs) laser to create localized small holes in the membranes of targeted cells to develop a virus-free technique to allow transfer of genetic material for treating these cancer cells with high efficiency and minimal collateral damage. This plasmonic enhanced fs laser process is efficient and highly selective with high cell viability, up to 90%. An optimum perforation rate with efficient molecule uptake was found for different types of gold nanostructures, spherical (100-200nm) and rod shaped (10x40nm).

Plasmonic manipulations of biomolecular targets using single-femtosecond pulses

Paper 7911-19 of Conference 7911
Date: Sunday, 23 January 2011
Time: 4:30 PM – 4:50 PM

Author(s): Gili Bisker, Limor Minai, Dvir Yelin, Technion-Israel Institute of Technology (Israel)
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Gold nanoparticles play an important role in biomedical research due to their unique optical properties and high biocompatibility. In this work, the effects of plasmonic resonance in gold nanoparticles were used to alter the structure and function of various types of biomolecules. We show a significant decrease in fluorescence of a solution of green fluorescence protein and 20 nm gold nanoparticles, which was resonantly irradiated with a single 50 fs long pulse. Consequent gel electrophoresis confirmed the dissociation of the protein. Experiments with other proteins indicated that different experimental parameters are required for their function loss and fragmentation.

Effects of femtosecond laser radiation on blood cell suspensions

Paper 7901-19 of Conference 7901
Date: Sunday, 23 January 2011
Time: 5:15 PM – 5:30 PM

Author(s): Tatyana Genning, Ulyanovsk State Univ. (Russian Federation); Alexej A. Sysoliatin, A. M. Prokhorov General Physics Institute (Russian Federation); Tatyana Abakumova, Dinara Arslanova, Olga Voronova, Igor Zolotovsky, Vladimir Ostatochnikov, Marina Yavtushenko, Ulyanovsk State Univ. (Russian Federation)
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High peak intensity of femtosecond laser radiation may be the cause of loss of cells, though the reasons of it may be different: from thermocoagulation of membrane protein up to injuries of genetic cell's apparatus. In the experiment we used red blood cells (Er) of mammals as a classic model of membrane and polymorphonuclear white blood cells (Hf) as a valuable cells with arranged genetic apparatus.

Femtosecond laser-induced protein crystallization in a gel solution

Paper 7937-18 of Conference 7937
Date: Sunday, 23 January 2011
Time: 5:15 PM – 5:40 PM

Author(s): Ryota Murai, Osaka Univ. (Japan); Hiroshi Y. Yoshikawa, Ruprecht-Karls-Univ. Heidelberg (Germany); Yoshinori Takahashi, Mihoko Maruyama, Shigeru Sugiyama, Osaka Univ. (Japan); Gen Sazaki, Hokkaido Univ. (Japan); Adachi Hiroaki, Kazufumi Takano, Hiroyoshi Matsumura, Osaka Univ. (Japan); Satoshi Murakami, Tokyo Institute of Technology (Japan); Tsuyoshi Inoue, Yusuke Mori, Osaka Univ. (Japan)
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We have previously developed a new technique for control of protein nucleation by femtosecond laser irradiation. The fast fluorescence imaging of the protein molecules revealed that cavitation bubbles created high-concentration regions at the focal point, which could be the trigger for nucleation. Futhermore, We found that the use of a gel solution enhanced femtosecond laser-induced nucleation and produced lysozyme crystals at three to five times lower supersaturation than those by the femtosecond laser or agarose alone. The lower diffusions of protein molecules in agarose gel retained the high-concentration regions for a longer time, and facilitated the nucleation.

Active surface-enhanced Raman scattering substrates based on the photoreduction mechanism of silver nanoparticles fabricated by femtosecond laser direct writing

Paper 7911-50 of Conference 7911
Date: Sunday, 23 January 2011
Time: 5:30 PM

Author(s): Hsing-Ying Lin, Chen-Han Huang, National Cheng Kung Univ. (Taiwan)
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A simple and single-step approach to fabricate silver nanoparticles in desired patterns on arbitrary material substrates via the photoreduction process by femtosecond laser direct writing is investigated. The central wavelength, repetition rate, and pulse width of fs laser are 800 nm, 80 MHz, and 120 fs, respectively. The fabrication laser power is tested from 0.1~2 W and tested concentration of AgNO3 solution is from 0.01~0.1 M. Results demonstrate that Ag nanoparticles are densely and uniformly distributed on specimen surfaces where the particle density is suitable to form lots "hot spots" to significantly enhance localized electric fields for Raman signal detections.

Direct laser written waveguide coupler with an optically-tunable splitting ratio

Paper 7925-19 of Conference 7925
Date: Monday, 24 January 2011
Time: 8:50 AM – 9:10 AM

Author(s): Martin Ams, Robert J. Williams, Michael J. Withford, CUDOS @ Macquarie (Australia)
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We report on the application of the femtosecond laser direct-write technique to create 2x2 waveguide couplers with optically-tunable splitting ratios. The device was inscribed inside ytterbium-doped phosphate glass. Tuning of the coupling ratio at 1550nm is achieved through resonant excitation of the ytterbium ions, which shifts the refractive index through heating and the direct pumping of a saturable absorption (Kramers-Krönig causality). Initial experiments/modelling demonstrate that a reversible change in splitting ratio greater than 20% is possible (i.e. 50:50 to 30:70) using <500mW of injected pump light. The implications for reconfigurable logic gates in quantum information systems will be discussed.

From multi kW continuous wave to multi MW femtosecond pulses: recent developments exploiting disk laser technology

Paper 7912-8 of Conference 7912
Date: Monday, 24 January 2011
Time: 8:50 AM – 9:10 AM

Author(s): Sascha Weiler, Marco Holzer, TRUMPF Laser- und Systemtechnik GmbH (Germany)
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Disk lasers combine high efficiency, excellent beam quality, high average and/or peak power with moderate cost and high reliability at multiple wavelengths, ranging from the infrared over the green to the ultraviolet. The demonstrated infrared average powers range from tens of kW in CW operation over >1 kW in ns pulses to >100 W in ps pulses and > 70 W in fs pulses. Wavelength conversion for nearly all modes of operation, e.g. 700 W@515nm in ns pulses, enlarges the fields of applications, making the disk technology today's most versatile laser platform.

Influence of laser parameters and staining on femtosecond laser-based intracellular nanosurgery

Paper 7897-3 of Conference 7897
Date: Monday, 24 January 2011
Time: 8:50 AM – 9:10 AM

Author(s): Kai Kuetemeyer, Rachid Rezgui, Holger Lubatschowski, Alexander Heisterkamp, Laser Zentrum Hannover e.V. (Germany)
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Femtosecond laser-based intracellular nanosurgery has become an important tool in cell biology, albeit the mechanisms are largely unknown. Here, we present our experimental study on the influence of laser parameters and staining on the intracellular ablation threshold in the low-density plasma regime. We found that the ablation effect of pulse trains resulted from the accumulation of single-shot multiphoton-induced photochemical effects finished within a few nanoseconds. Furthermore, fluorescence staining of subcellular structures before surgery significantly decreased the ablation threshold. Based on our findings, we propose that dye molecules are the major source for providing seed electrons for the ionization cascade.

50 W thin-disk laser with variable pulse duration

Paper 7912-9 of Conference 7912
Date: Monday, 24 January 2011
Time: 9:10 AM – 9:30 AM

Author(s): Mikhail A. Larionov, Friedrich Dausinger, Dausinger + Giesen GmbH (Germany)
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The laser system based on a Yb:YAG thin-disk regenerative amplifier has been developed. The average output power of 50 W is sufficient or micromachinnig applications. The pulse duration is variable between sub-picosends and microseconds at repetition rates up to 1 MHz. The amplifier cavity is operated with different seed sources and in different operation modes - regenerative amplification, cavity dumping, Q-switching - in order to address the broad spectrum of pulse durations. The output beam is always defined by the amplifier cavity and remains the same for all pulse durations, allowing for a fair comparison of micromachining results.

Absorption of femtosecond laser pulse in fused silica: experiments and modelling

Paper 7920-2 of Conference 7920
Date: Monday, 24 January 2011
Time: 9:10 AM – 9:30 AM

Author(s): Nadezda Varkentina, Olivier P. Uteza, Benoît Chimier, Nicolas Sanner, Lasers, Plasmas et Procédés Photoniques (France); Tatiana E. Itina, Lab. Hubert Curien (France); Marc L. Sentis, Lasers, Plasmas et Procédés Photoniques (France)
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We present the experimental results of reflection, transmission and absorption siglans of fused silica under single pulse femtosecond laser irradiation as a function of fluence.The experimental curves are accompanied by a modelling which takes into account the photoionization and avalanche ionization mechanizms.We outline the distinction between the ablation and the damage thresholds for dielectric materials.From the model we deduce the crater depth to the applied fluence.We further compare it to experimental data measured by atomic force microscopy technique.

Determining properties of spindle microtubules with femtosecond nanosurgery

Paper 7897-4 of Conference 7897
Date: Monday, 24 January 2011
Time: 9:10 AM – 9:30 AM

Author(s): Valeria Nuzzo, Jan Brugués, Daniel J. Needleman, Eric Mazur, Harvard Univ. (United States)
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In eukaryotic cells, the spindle ensures the faithful segregation of the genetic material during cell division. In this study we use femtosecond nanosurgery to quantitatively measure parameters describing the metaphase spindle. We selectively cut microtubules of metaphase spindles assembled from Xenopus egg extracts. After the cut, microtubules depolymerize rapidly. Analysis of the time-lapse imaging reveals the depolymeration dynamics and allows determining the length distribution of the microtubules. We show that the average length of microtubules in metaphase spindles increases from the pole towards the equator. We show that a spatially variable nucleation of microtubules can explain our measurements.

Ultrafast dynamics of femtosecond laser-induced nanostructure formation on metals

Paper 7937-22 of Conference 7937
Date: Monday, 24 January 2011
Time: 9:15 AM – 9:40 AM

Author(s): Chunlei Guo, Univ. of Rochester (United States)
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In this talk, I will discuss our recent study on femtosecond laser-induced nanostructures on metals. We found that nanostructure formation can vary greatly among different metals, and the differences are attributed to the competition of ultrafast processes involved, including electron-phonon coupling and hot electron diffusion, following femtosecond laser heating of metals.

Phase-cycling coherent anti-Stokes Raman scattering using shaped femtosecond laser pulses

Paper 7903-25 of Conference 7903
Date: Monday, 24 January 2011
Time: 9:17 AM – 9:29 AM

Author(s): Baolei Li, Warren S. Warren, Sr., Martin C. Fischer, Duke Univ. (United States)
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We demonstrate a homodyne coherent anti-Stokes Raman scattering (CARS) technique based on femtosecond laser pulse shaping. This technique utilizes fast phase cycling to extract nonlinear Raman signatures with a self-generated reference signal (local oscillator). The local oscillator is generated at the focal point within the sample and its phase is intrinsically stable relative to the Raman signal. We can therefore retrieve phase information from the Raman signal and can suppress the ubiquitous non-resonant background.

3D patterning at the nanoscale of fluorescent emitters in glass

Paper 7925-21 of Conference 7925
Date: Monday, 24 January 2011
Time: 9:30 AM – 9:50 AM

Author(s): Matthieu Bellec, Arnaud Royon, Kevin Bourhis, Gautier Papon, Bruno Bousquet, Thierry Cardinal, Lionel Canioni, Univ. Bordeaux 1 (France)
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Three-dimensional fluorescent nanostructures are photo-induced by a near infrared high repetition rate femtosecond laser in a silver containing femto-photo-luminescent glass. By adjusting the laser dose (fluence, number of pulses and repetition rate), these stabilized intense fluorescent structures, composed of silver clusters, can be achieved with a perfect control of the luminescence intensity, the emission spectrum and the spatial distribution at the nanometer scale. This novel approach opens the way to the fabrication of stable fluorescent nanostructures in three dimensions in glass for applications in photonics and optical data storage.

New step towards the future perennial high capacity optical recording medium

Paper 7925-22 of Conference 7925
Date: Monday, 24 January 2011
Time: 9:50 AM – 10:10 AM

Author(s): Arnaud Royon, Kevin Bourhis, Matthieu Bellec, Gautier Papon, Bruno Bousquet, Yannick Deshayes, Thierry Cardinal, Lionel Canioni, Univ. Bordeaux 1 (France)
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We report on three-dimensional optical recording by exploiting the fluorescence features of femtosecond-laser-induced silver clusters in glass. The fluorescence properties of these stable clusters are controlled and depend on the glass recording exposure conditions. The high dynamics of the fluorescence intensity permits the encoding of the information on tens of levels. The combination of a blue laser diode with a high numerical aperture focusing set-up, similar to the "Blu-ray" drive, enables the readout of the information inside the glass without cross-talk and photo-bleaching. This recording medium can be used to answer the societal problem of perennial high density data storage.

Breaking stress of glass welded with femtosecond laser pulses at high repetition rates

Paper 7925-24 of Conference 7925
Date: Monday, 24 January 2011
Time: 11:10 AM – 11:30 AM

Author(s): Sören Richter, Sven Döring, Friedrich-Schiller-Univ. Jena (Germany); Thomas Peschel, Ramona Eberhardt, Fraunhofer-Institut für Angewandte Optik und Feinmechanik (Germany); Stefan Nolte, Friedrich-Schiller-Univ. Jena (Germany); Andreas Tünnermann, Friedrich-Schiller-Univ. Jena (Germany) and Fraunhofer-Institut für Angewandte Optik und Feinmechanik (Germany)
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We report measurements of the breaking stress of glass substrates welded with ultrashort laser pulses. The laser pulses at repetition rates in the MHz range are focused at the interface between two substrates, resulting in multiphoton absorption and heat accumulation from successive pulses. The following local melting and subsequent resolidification leads to the formation of bonds at the interface. This results in a very flexible and local bonding process. The breaking stress achievable is discussed in detail in dependence of the laser and material parameters. Also the influence of the induced stress during the writing process will be explained.

Non-invasive optical modulation of local vascular permeability

Paper 7897-9 of Conference 7897
Date: Monday, 24 January 2011
Time: 11:20 AM – 11:40 AM

Author(s): Myunghwan Choi, Chulhee Choi M.D., KAIST (Korea, Republic of)
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For a systemically administered drug to act, it first needs to cross the vascular wall. This step represents a bottleneck for drug development, especially in the brain or retina, where tight junctions between endothelial cells form physiological barriers. Here, we demonstrate that femtosecond pulsed laser irradiation focused on the blood vessel wall induces transient permeabilization of plasma. Nonlinear absorption of the pulsed laser enabled the noninvasive modulation of vascular permeability with high spatial selectivity in three dimensions. By combining this method with systemic injection, we could locally deliver molecular probes in various tissues, such as brain cortex, meninges, striated muscle, and bone. We suggest this method as a novel delivery tool for molecular probes or drugs.

The influence of glass structure on femtosecond laser micro machining of waveguide amplifiers inside bulk Er-Yb doped polyphosphate glass

Paper 7925-25 of Conference 7925
Date: Monday, 24 January 2011
Time: 11:30 AM – 11:50 AM

Author(s): Luke B. Fletcher, Neil Troy, Jon J. Witcher, Denise M. Krol, Univ. of California, Davis (United States); Richard K. Brow, Missouri Univ. of Science and Technology (United States)
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Photo-induced modifications inside active phosphate glass can be used to fabricate waveguide lasers and amplifiers. Single scan waveguides have been fabricated inside Er-Yb doped zinc polyphosphate glasses using tightly focused femtosecond laser pulses from a Ti:Saphire, 1 kHz laser system. A variety of Er-Yb zinc phosphate glass compositions with [O]/[P] ratios of 3.25 has demonstrated positive refractive index changes after the absorption of focused fs-laser pulses that can be used to fabricate waveguide amplifiers. Laser writing parameters, waveguide insertion losses and gain characteristics have been measured and optimized. Laser-induced structural changes have been studied using confocal fluorescence and Raman microscopy.

Course: Micromachining with Femtosecond Lasers

Date: Monday, 24 January 2011
Time: 1:30 PM – 5:30 PM

Instructor(s): Stefan Nolte, Friedrich-Schiller-Univ. Jena (Germany); Christopher B. Schaffer, Cornell Univ. (United States)
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This course provides attendees with the knowledge necessary to understand and apply femtosecond laser pulses for micromachining tasks in a variety of materials. Emphasis will be placed on developing a fundamental understanding of how femtosecond pulses interact with the sample. From this knowledge, the advantages and limitations of femtosecond lasers for various micromachining tasks can be readily understood. Examples will be given in the micromachining of the surface of metals, semiconductors, and transparent materials, as well as the formation of photonic and microfluidic devices in the bulk of transparent materials.

Differential-CARS microscopy with linearly chirped femtosecond laser pulses

Paper 7903-50 of Conference 7903
Date: Monday, 24 January 2011
Time: 4:53 PM – 5:05 PM

Author(s): Wolfgang Langbein, Israel Rocha-Mendoza, Peter Watson, Paola Borri, Cardiff Univ. (United Kingdom)
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We demonstrate frequency differential CARS (D-CARS) using femtosecond laser pulses linearly chirped by glass elements of high group-velocity dispersion. By replicating the Pump-Stokes pair into a pulse train at twice the laser repetition rate, and controlling the instantaneous frequency difference by glass dispersion, we adjust the Raman frequency probed by each pair in an intrinsically stable way. The resulting CARS intensities are detected simultaneously by a single photomultiplier as sum and difference using lock-in detection. We demonstrate imaging of polymer beads and living cells with strongly suppressed non-resonant background. We also show D-CARS using a single femtosecond laser source.

Sub-100-nm material processing with sub-15-femtosecond picojoule near-infrared laser pulses

Paper 7903-54 of Conference 7903
Date: Tuesday, 25 January 2011
Time: 8:00 AM – 8:20 AM

Author(s): Karsten Koenig, Aisada A. Uchugonova, Martin H. Straub, Huijing Zhang, Maziar Afshar, Dara Feili, Helmut Seidel, Univ. des Saarlandes (Germany)
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Ultrabroad band in situ 12 femtosecond near infrared laser pulses at transient TW/cm2 intensities and low picojoule pulse energies (mean powers < 20 mW at 85 MHz repetition rate) have been used to perform 3D material nanoprocessing based on multiphoton ionization and plasma formation. Cut sizes of sub-wavelength, sub-100 nm which is far beyond the Abbe diffraction have been realized without any collateral damage effect in silicon wafers, photoresists, glass, metals, and biological targets. Acknowledgments: The authors wish to thank the German Science Foundation (Key Program 1327) for financial support.

Nanosurgery with near-infrared femtosecond and picosecond laser pulses

Paper 7903-55 of Conference 7903
Date: Tuesday, 25 January 2011
Time: 8:20 AM – 8:40 AM

Author(s): Aisada A. Uchugonova, Huijing Zhang, Karsten Koenig, Univ. des Saarlandes (Germany)
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Laser-assisted surgery based on multiphoton absorption of NIR light has great potential for high precision surgery at various depths within the cells and tissues. Especially such non-contact method supports contamination-free cell surgery. Here we apply femtosecond laser scanning microscopes for sub-100 nm surgery of human cells and metaphase chromosomes. A mode-locked 85 MHz Ti:Sapphire laser with an M-shaped ultrabroad band spectrum (maxima: 770 nm/830 nm) with an in situ pulse duration at the target of 12 femtoseconds up to 3 picoseconds due to the introduction of chirped mirrors, flint glass wedges, and glass blocks was employed. The results of laser nanoprocessing in cell/chromosome structures have been quantified by atomic force microscopy (AFM) and electron microscopy. These studies demonstrate the potential of extreme ultrashort femtosecond laser pulses at low mean milliwatt powers for sub-100 nm surgery.

Highly flexible ultrafast laser system with 220W average power

Paper 7912-23 of Conference 7912
Date: Tuesday, 25 January 2011
Time: 8:30 AM – 8:50 AM

Author(s): Torsten G. Mans, Jan Dolkemeyer, AMPHOS GmbH (Germany); Peter Russbueldt, Fraunhofer-Institut für Lasertechnik (Germany); Claus Schnitzler, AMPHOS GmbH (Germany)
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We present a flexible ultrafast laser amplifier system based on InnoSlab technology with an average power exceeding 200W. The pulse duration of the system can be continuously tuned between 530fs and 5.4ps limited by the amplification bandwidth of Yb:YAG and the currently used seed source. The repetition rate can be varied from 26.6MHz down to 1MHz. Without the need of compression of the high power beam some 10ตJ are accessible before first signs of self-phase modulation avoid operation with low spectral bandwidth (<3nm) close to the transform limit. Beam quality is measured to be near the diffraction limit (M2<=1.3).

Colorizing of the stainless steel surface by single-beam direct femtosecond laser writing

Paper 7920-34 of Conference 7920
Date: Tuesday, 25 January 2011
Time: 8:50 AM – 9:10 AM

Author(s): Md. S. Ahsan, KAIST (Korea, Republic of) and Khulna Univ. (Bangladesh); Yeong Gyu Kim, Man Seop Lee, KAIST (Korea, Republic of)
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We report on the colorizing of the stainless steel surface by femtosecond laser induced periodic microholes or microgratings on the sample surface; colorizing of metal surface by periodic microholes is achieved for the first time. The laser modified stainless steel surfaces show different colors under different incident or azimuthal angles of the incident light. Dependence of metal color on azimuthal angles is reported for the first time. Under different incident or azimuthal angles, different wavelength of light is trapped on the surface due to the excitation of surface plasmons (SPs); light of other wavelengths react naturally and contributes for the color change of the stainless steel surface.

Colorizing of the stainless steel surface by single-beam direct femtosecond laser writing

Paper 7925-34 of Conference 7925
Date: Tuesday, 25 January 2011
Time: 8:50 AM – 9:10 AM

Author(s): Md. S. Ahsan, KAIST (Korea, Republic of) and Khulna Univ. (Bangladesh); Yeong Gyu Kim, Man Seop Lee, KAIST (Korea, Republic of)
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We report on the colorizing of the stainless steel surface by femtosecond laser induced periodic microholes or microgratings on the sample surface; colorizing of metal surface by periodic microholes is achieved for the first time. The laser modified stainless steel surfaces show different colors under different incident or azimuthal angles of the incident light. Dependence of metal color on azimuthal angles is reported for the first time. Under different incident or azimuthal angles, different wavelength of light is trapped on the surface due to the excitation of surface plasmons (SPs); light of other wavelengths react naturally and contributes for the color change of the stainless steel surface.

Femtosecond pump-probe imaging reveals chemical and architectural changes in human melanoma

Paper 7903-61 of Conference 7903
Date: Tuesday, 25 January 2011
Time: 9:55 AM – 10:10 AM

Author(s): Thomas E. Matthews, Ivan Piletic, Maria Angelica Selim, Mary Jane Simpson, Warren S. Warren, Sr., Duke Univ. (United States)
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We have developed a nonlinear imaging method, based on pump-probe spectroscopy in a scanning laser microscope, to directly discriminate and image the two varieties of melanin found in human skin: eumelanin and pheomelanin. We imaged a variety of excised pigmented lesions including benign nevi, compound and dysplastic nevi, malignant melanomas and pigmented basal cell carcinomas. It was found that the melanin in melanomas and carcinomas was predominantly eumelanin, while the surrounding normal tissue and benign lesions were more pheomelanic. We extended this technique to H&E stained slides, allowing co-localization with structural features and making it compatible with traditional pathology samples.

An investigation of piezoelectric cutting by femtosecond laser

Paper 7920-19 of Conference 7920
Date: Tuesday, 25 January 2011
Time: 10:00 AM – 10:20 AM

Author(s): Yoan Di Maio, Eric Audouard, Jean-Philippe Colombier, Univ. Jean Monnet Saint-Etienne (France); Paul Cazottes, José Beitia, Sagem Defense Securite (France)
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The cutting of the piezoelectric ceramic Pb(ZrxTi1-x)O3 (PZT) with femtosecond lasers for high technology applications allows better results compared to nowadays techniques, but have revealed several undesired behaviours, although this techniques seems well suited for more common materials. In this study, we carry out an investigation to characterize the PZT through this radiation by determining both the ablation rate and the ablation threshold and an identification of these laser-induced phenomena such as rippled-like nanostructurations or craking. At last, the control of these effects will allow performing uniform processes of the machined pieces.

An investigation of piezoelectric cutting by femtosecond laser

Paper 7925-19 of Conference 7925
Date: Tuesday, 25 January 2011
Time: 10:00 AM – 10:20 AM

Author(s): Yoan Di Maio, Eric Audouard, Jean-Philippe Colombier, Univ. Jean Monnet Saint-Etienne (France); Paul Cazottes, José Beitia, Sagem Defense Securite (France)
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The cutting of the piezoelectric ceramic Pb(ZrxTi1-x)O3 (PZT) with femtosecond lasers for high technology applications allows better results compared to nowadays techniques, but have revealed several undesired behaviours, although this techniques seems well suited for more common materials. In this study, we carry out an investigation to characterize the PZT through this radiation by determining both the ablation rate and the ablation threshold and an identification of these laser-induced phenomena such as rippled-like nanostructurations or craking. At last, the control of these effects will allow performing uniform processes of the machined pieces.

Time-resolved x-ray scattering

Paper 7937-40 of Conference 7937
Date: Tuesday, 25 January 2011
Time: 11:10 AM – 11:35 AM

Author(s): Matias Bargheer, Univ. Potsdam (Germany)
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Ultrafast x-ray diffraction has become more and more prevalent in various scientific disciplines that are interested in directly observing atomic motion in real time. The timescale, amplitude and phase of collective atomic motion can be determined with high accuracy, even when the induced amplitude is smaller than thermal fluctuations. The structural rearrangements induced by an ultrafast stimulus (charge carriers excited or heat deposited by a laser pulse) can be recorded in real time. This yields additional information of physical properties such as the electron-phonon or spin-lattice interaction. We discuss examples including the direct observation of indirect magneto-electric coupling in oxides.

Microfluidic chips integrated with different functions by femtosecond laser for mechanism study of Phormidium gliding

Paper 7929-20 of Conference 7929
Date: Tuesday, 25 January 2011
Time: 11:30 AM – 11:50 AM

Author(s): Yasutaka Hanada, Koji Sugioka, Ikuko S. Ishikawa, Hiroyuki Kawano, Atsushi Miyawaki M.D., Katsumi Midorikawa, RIKEN (Japan)
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We fabricate glass microchips by femtosecond laser (fs) for mechanism study of Phormidium gliding to a seedling root. The microchip reduced the microscopic observation time of the gliding movement. Additionally, the Phormidium always glided to the reservoir in which the root was introduced, which suggests some attractants are secreted from the root for the gliding. Then, the microchips integrated with waveguides written by the fs laser were used to identify the attractant by optical means. Meanwhile, optical filters of visible light with different transmission were formed around the microchannel for the investigation of the light intensity required for the gliding.

All quantum dot based femtosecond VECSEL

Paper 7919-33 of Conference 7919
Date: Tuesday, 25 January 2011
Time: 2:45 PM – 3:00 PM

Author(s): Martin Hoffmann, Oliver D. Sieber, Wolfgang P. Pallmann, Valentin J. Wittwer, Yohan Barbarin, Thomas Südmeyer, Ursula Keller, ETH Zurich (Switzerland); Igor L. Krestnikov, Sergey S. Mikhrin, D. A. Livshits, Innolume GmbH (Germany); Graeme Malcolm, Craig Hamilton, M Squared Lasers Ltd. (United Kingdom)
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Using quantum well gain materials, ultrafast VECSELs have achieved higher output powers (2.1 W) and shorter pulses (60 fs) than any other semiconductor laser. Quantum dot (QD) gain materials offer a larger inhomogeneously broadened bandwidth potentially supporting shorter pulse durations. We demonstrate the first femtosecond QD-based VECSEL using a QD-SESAM for modelocking, obtaining 63 mW at 3.2 GHz in 780-fs pulses at 960 nm. In cw operation we obtained 5.2 W using an intra cavity diamond heat spreader, which has been the highest output power from a QD-VECSEL so far. Further power scaling is thus expected also for modelocked operation.

Femtosecond laser nanofabrication of metal structures through multiphoton photoreduction

Paper 7927-14 of Conference 7927
Date: Tuesday, 25 January 2011
Time: 4:00 PM – 4:20 PM

Author(s): Kevin Vora, SeungYeon Kang, Michael Moebius, Eric D. Mazur, Harvard Univ. (United States)
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We present an ultrafast laser technique for direct-writing gold and silver structures of tunable dimensions. By utilizing nonlinear optical interactions between chemical precursors and femtosecond pulses, we limit metal-ion photoreduction processes to focused spots smaller than that of the diffraction-limit. This creates metal nanostructures in a focal volume that can be rapidly scanned in 3D. By varying the solution chemistry and laser pulse parameters, we demonstrate morphological control of the resulting structures. We fabricate grid and woodpile patterns over hundreds of micrometers in dimensions. We show the process is scalable and possesses optical characteristics suitable for SERS or metamaterial applications.

Optical control of urination in neurogenic bladder using femtosecond-pulsed laser

Paper 7897-39 of Conference 7897
Date: Tuesday, 25 January 2011
Time: 4:20 PM – 4:40 PM

Author(s): Jonghee Yoon, Myunghwan Choi, Chulhee Choi M.D., KAIST (Korea, Republic of)
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Even though catheterization or electric stimulation are used for treatment of neurogenic bladder, invasiveness and inconvenience of these approaches prompt us to develop a new possible therapeutic method to control urination by using optical stimulation. The optical method using femtosecond pulsed laser (FSPL) has advantages of focused and subsurface stimulation. Irradiation of FSPL induced a rapid increase of intracellular calcium level followed by contraction of primary cultured human bladder smooth muscle cells. Short exposure of bladder detrusor ex-vivo to FSPL also induced a controlled contraction of detrusor. Collectively, we propose that FSPL can be considered as a potential therapeutic approach for intractable neurogenic bladder.

Uniform near-field nanopatterning due to the field distribution control by oblique femtosecond laser irradiation to nanoparticles

Paper 7925-25 of Conference 7925
Date: Tuesday, 25 January 2011
Time: 4:20 PM – 4:40 PM

Author(s): Tomoya Miyanishi, Mitsuhiro Terakawa, Minoru Obara, Keio Univ. (Japan)
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We present near-field optical properties around silica, silicon and gold nanoparticles on a silicon substrate by oblique incidence femtosecond laser for nanohole fabrication. We investigated localized near-field distribution of silica and silicon nanoparticles by using oblique irradiation. With silica particles, the position of the peak intensity point is controllable by controlling the incidence angle. With silicon particles, the distribution of the concentrated energy obtained with silicon nanoparticles is similar to that of gold nanoparticles, suggesting that silicon nanoparticles show an intermediate optical property between silica and gold nanoparticles.

Uniform near-field nanopatterning due to the field distribution control by oblique femtosecond laser irradiation to nanoparticles

Paper 7920-25 of Conference 7920
Date: Tuesday, 25 January 2011
Time: 4:20 PM – 4:40 PM

Author(s): Tomoya Miyanishi, Mitsuhiro Terakawa, Minoru Obara, Keio Univ. (Japan)
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We present near-field optical properties around silica, silicon and gold nanoparticles on a silicon substrate by oblique incidence femtosecond laser for nanohole fabrication. We investigated localized near-field distribution of silica and silicon nanoparticles by using oblique irradiation. With silica particles, the position of the peak intensity point is controllable by controlling the incidence angle. With silicon particles, the distribution of the concentrated energy obtained with silicon nanoparticles is similar to that of gold nanoparticles, suggesting that silicon nanoparticles show an intermediate optical property between silica and gold nanoparticles.

169 GHz repetition rate passively harmonically mode-locked VECSEL emitting 265 fs pulses

Paper 7919-36 of Conference 7919
Date: Tuesday, 25 January 2011
Time: 4:30 PM – 4:45 PM

Author(s): Adrian H. Quarterman, Keith G. Wilcox, Alex Perevedentsev, Vasilis Apostolopoulos, Zakaria Mihoubi, Aaron L. Chung, Univ. of Southampton (United Kingdom); Harvey E. Beere, Ian Farrer, David A. Ritchie, Univ. of Cambridge (United Kingdom); Anne C. Tropper, Univ. of Southampton (United Kingdom)
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Here we report a passively mode-locked femtosecond VECSEL emitting 265 fs duration pulses at a repetition rate of 169 GHz and with a centre wavelength of 1030 nm and an output power of 20 mW. The laser is harmonically mode-locked by introducing an intracavity sapphire etalon which acts as a coupled cavity. RF spectra confirm stable harmonic modelocking when the fundamental cavity length is adjusted such that it matches a multiple of the etalon thickness, but the low intracavity pulse energies result in a tendency towards Q-switched modelocking.

High temperature multiparameter sensor with 1000ฐC capability

Paper 7934-13 of Conference 7934
Date: Tuesday, 25 January 2011
Time: 4:40 PM – 5:00 PM

Author(s): Robert B. Walker, Dan Grobnic, Stephen J. Mihailov, Communications Research Ctr. Canada (Canada)
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Spectral characteristics of fiber Bragg gratings are affected by both strain and temperature. While this makes gratings useful for sensing, care must be taken to ensure adequate discrimination between spectral shifts associated with strain and those due to changes in temperature. Recently, monitoring of tilted grating cladding modes has been utilized for this purpose. The drawback of presently published examples is that none offer such measurement capabilities at high temperature (800 ~ 1000 ฐC). In this paper, by exploiting the characteristics of Type II fs-IR written gratings, we present such an example. Achieving similar responsivity with significantly improved thermal durability.

No effect of femtosecond laser pulses on DNA, protein, M13, or E. coli

Paper 7897-41 of Conference 7897
Date: Tuesday, 25 January 2011
Time: 5:00 PM – 5:20 PM

Author(s): Jeffrey C. Wigle, Eric A. Holwitt, Katharine E. Sheldon, U.S. Air Force (United States); Larry E. Estlack, Conceptual MindWorks, Inc. (United States); Gary D. Noojin, TASC, Inc. (United States); Benjamin A. Rockwell, U.S. Air Force (United States)
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We were unable to reproduce published inactivation results, or show any interaction, between 90 femtosecond (fs) pulses of 850 nm or 425 nm laser radiation and buffer/water, DNA, protein, M13 bacteriophage or E. coli. We examined purified plasmid DNA (pUC19), bovine serum albumin, M13 viability, and DNA and coat proteins extracted from M13 at irradiances of up to 120 MW/cm2. Exposures of up 1 GW/cm2 at 850 nm had no effect on the viability of E. coli. Peroxynitrite, known to be toxic, to cause single strand breaks in DNA, and fragment proteins in vitro gave positive results in all assays.


Optimization methods of hologram for holographic femtosecond laser processing

Paper 7920-28 of Conference 7920
Date: Tuesday, 25 January 2011
Time: 5:20 PM – 5:40 PM

Author(s): Yoshio Hayasaki, Satoshi Hasegawa, Utsunomiya Univ. (Japan)
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In holographic femtosecond laser processing, a critical issue is to precisely control the intensities of the diffraction peaks generated by a computer-generated hologram (CGH) displayed on a liquid crystal spatial light modulator. We developed some design methods of the CGH. We developed a method that the CGH was optimized with based on an optical measurement of the diffraction peak intensities. Recently we also developed the second harmonic optimization method based on the second harmonic generations induced by the parallel femtosecond beam. In our presentation, our recent progresses of the CGH optimization for holographic femtosecond laser processing are demonstrated.

Optimization methods of hologram for holographic femtosecond laser processing

Paper 7925-28 of Conference 7925
Date: Tuesday, 25 January 2011
Time: 5:20 PM – 5:40 PM

Author(s): Yoshio Hayasaki, Satoshi Hasegawa, Utsunomiya Univ. (Japan)
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In holographic femtosecond laser processing, a critical issue is to precisely control the intensities of the diffraction peaks generated by a computer-generated hologram (CGH) displayed on a liquid crystal spatial light modulator. We developed some design methods of the CGH. We developed a method that the CGH was optimized with based on an optical measurement of the diffraction peak intensities. Recently we also developed the second harmonic optimization method based on the second harmonic generations induced by the parallel femtosecond beam. In our presentation, our recent progresses of the CGH optimization for holographic femtosecond laser processing are demonstrated.

Comparative numerical study of efficiency of energy deposition in femtosecond microfabrication with fundamental and second harmonics of Yb-doped fiber laser

Paper 7914-111 of Conference 7914
Date: Tuesday, 25 January 2011
Time: 6:00 PM

Author(s): Alexandr Dostovalov, Sergey A. Babin, Institute of Automation and Electrometry (Russian Federation); Vladimir K. Mezentsev, Mykhaylo Dubov, Mandana Baregheh, Aston Univ. (United Kingdom)
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We present the results of comparative numerical study of energy deposition in single shot femtosecond laser inscription for fundamental and second harmonic of Yb-doped fiber laser. We have found that second harmonic is more efficient in terms of amount of absorbed energy which leads to lower inscription threshold. Hence this regime is more attractive for applications in femtosecond laser microfabrication.

Fabrication of gold-platinum alloy nanoparticles by high-intensity laser irradiation of aqueous solution

Paper 7922-19 of Conference 7922
Date: Tuesday, 25 January 2011
Time: 6:00 PM

Author(s): Takahiro Nakamura, Yuliati Herbani, Shunichi Sato, Tohoku Univ. (Japan)
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Gold-platinum alloy nanoparticles were directly fabricated by high-intensity femtosecond laser irradiation of mixed aqueous solutions of auric and platinum ions. The resulting particles were characterized by UV-visible spectroscopy, TEM and XRD. The position of XRD peaks of the particles shifted from that of pure gold to platinum, and XRD peaks of the particles prepared in the solutions with a certain mixing ratio of auric and platinum ions were observed between the peak positions of gold and platinum. This demonstrates bimetallic gold-platinum nanoparticles are successfully fabricated only by laser irradiation of mixed aqueous solution of auric and platinum ions.

Invisible two-dimensional barcode fabrication inside a synthetic silica glass by femtosecond laser processing using a computer-generated hologram

Paper 7925-43 of Conference 7925
Date: Tuesday, 25 January 2011
Time: 6:00 PM

Author(s): Hayato Kawashima, Masahiro Yamaji, Jun'ichi Suzuki, Shuhei Tanaka, New Glass Forum (Japan)
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We report an invisible two-dimensional (2D) barcode embedded into a synthetic silica glass by femtosecond laser processing using a CGH that generates a spatially extended femtosecond pulse beam in the depth direction. When we illuminate the irradiated 2D barcode pattern with a 254 nm ultraviolet light, a red photoluminescence (PL) is observed, and we can read it by using a CMOS camera and image processing technology. This work provides a novel barcode fabrication method by femtosecond laser processing using a CGH and a barcode reading method by a red PL.

Near damage threshold micromachining on the chrome stainless mold steel using the femtosecond laser

Paper 7926-16 of Conference 7926
Date: Tuesday, 25 January 2011
Time: 6:00 PM

Author(s): Ho Lee, SangHoon Choi, Changwhan Kim, YounJung Park, Kyungpook National Univ. (Korea, Republic of); Ik-Bu Sohn, Gwangju Institute of Science and Technology (Korea, Republic of)
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In spite of its advantage over the long pulsed laser, the application of femtosecond laser on the metals especially on the stainless mold steel had been limited due to the high thermal diffusivity of the material. In this study, the femtosecond laser induced morphological changes on the stainless mold steel were studied, especially at near-damage threshold fluence regime. The stationary beam induced damage threshold and the morphology changes were examined using a scanning electron microscopy. The scanning beam induced morphological change were studied using various laser parameters including the pulse energy, scanning speed and the polarization of the beam.

Simulation the temperature increase in porcine cadaver iris during direct illumination by femtosecond laser pulses

Paper 7925-41 of Conference 7925
Date: Tuesday, 25 January 2011
Time: 6:00 PM

Author(s): Hui Sun, Ronald M. Kurtz M.D., Tibor Juhasz, Univ. of California, Irvine (United States)
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PURPOSE: we simulated the temperature rise in porcine cadaver iris during direct illumination by the laser. METHODS: The temperature increase induced by a 60 kHz iFS Advanced Femtosecond Laser (AMO Inc. Santa Ana, CA) in porcine cadaver iris was simulated using COMSOL (Comsol Inc. MA) finite element software. RESULTS: Temperature increases up to 2.45 Celsius degree (corresponding to 2 microJ and 24 second illumination) were observed in the porcine cadaver iris from simulation with little variation in temperature profiles compared with specimens for the same laser energy illumination in experiment. CONCLUSIONS: The commercial iFS Advanced Femtosecond Laser does not present a safety hazard to the iris.

Solid state fs oscillators with direct laser-diode pumping

Paper 7912-80 of Conference 7912
Date: Tuesday, 25 January 2011
Time: 6:00 PM

Author(s): Guang-Hoon Kim, Uk-Song Kang, Elena G. Sall, Sergey A. Chizhov, Andrey Koulik, Korea Electrotechnology Research Institute (Korea, Republic of); Vladimir E. Yashin, S.I. Vavilov State Optical Institute (Russian Federation)
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We desceibeds the development of solid-state fs oscillators which are based on Yb:KYW with direct pumping by a semiconductor injection laser. Powerful laser-diode are pumping in the logitudinal direction. Femtosecond pulses are generated in the passive mode-locking by using a semiconductor saturable absorber. The oscillators can be used as a stand-alone source of femtosecond radiation pulses for material microprocessing and primary source for femtosecond laser amplification systems.

Synthesis of silicon fibrous nanoparticles aggregate structures using femtosecond laser radiation

Paper 7922-18 of Conference 7922
Date: Tuesday, 25 January 2011
Time: 6:00 PM

Author(s): Manickam Sivakumar, Ryerson Univ. (Canada) and Amrita Vishwa Vidyapeetham (India); Krishnan Venkatakrishnan, Bo Tan, Ryerson Univ. (Canada)
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Irradiation of silicon samples with femtosecond laser pulses at megahertz pulse repetition rate under ambient condition lead to the generation weblike fibrous nanostructure. Electron microscopy analysis revealed that the fibrous nanostructure is formed due to aggregation of nanoparticles of size varying between 2 to 40 nm. The amorphous nature of silicon nanoparticles present in the nanoparticles aggretae is confirmed by microraman analysis. The nanoparticles formation is explained by nucleation and condensation of vapour in the plasma plume generated during the irradiation process. This study provides evidence that femtosecond laser irradiation can be an ambient condition physical method for silicon fibrous nanoparticles aggregate structures generation.

Scaling high-power ultrafast VECSELs into the femtosecond regime

Paper 7919-25 of Conference 7919
Date: Tuesday, 25 January 2011
Time: 9:30 PM – 9:45 PM

Author(s): Oliver D. Sieber, Martin Hoffmann, Valentin J. Wittwer, Wolfgang P. Pallmann, Yohan Barbarin, Matthias C. Golling, Thomas Südmeyer, Ursula Keller, ETH Zurich (Switzerland)
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The combination of high output power and femtosecond pulses from VECSELs and MIXSELs would be very attractive for many applications. To explore the limitations, a quantitative understanding of the pulse formation processes is required. Our numerical simulations showed a good qualitative agreement with experimental results in the picosecond regime. By minimizing intracavity group delay dispersion (GDD) and improving gain bandwidth and SESAM parameters, our model predicts pulses as short as 750 fs. As a first step we minimized GDD with a top coating which provides values between ฑ10 fs2 over a range of 30 nm around the design wavelength.

Novel concept for long-haul ultrashort pulse fiber delivery without pre-chirping

Paper 7912-41 of Conference 7912
Date: Wednesday, 26 January 2011
Time: 8:20 AM – 8:40 AM

Author(s): Tuan Le, Gabriel Tempea, Andreas Stingl, FEMTOLASERS Produktions GmbH (Austria); Kim G. Jespersen, OFS Fitel Denmark ApS (Denmark); Karin Wiesauer, RECENDT GmbH (Austria)
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Ultrashort pulse fiber delivery for Ti:Sapphire lasers is basically restricted to distances below several meters which is due to the application of dispersion compensating devices that are not capable managing third and higher order material dispersion. By the use of a novel fiber delivery concept ultrashort laser pulses in the 800 nm wavelength range can now be transmitted over tens of meters without the need for any pulse pre-compression. For the first time a long-haul fiber delivery module will be demonstrated revealing its potential for remote imaging or THz spectroscopy with femtosecond laser pulses.

Broadband third-harmonic generation on interfaces using femtosecond pulses

Paper 7917-28 of Conference 7917
Date: Wednesday, 26 January 2011
Time: 8:50 AM – 9:10 AM

Author(s): Lino Misoguti, Emerson C. Barbano, Jonathas de Paula Siqueira, Cleber R. Mendonça, Sérgio C. Zilio, Univ. de São Paulo (Brazil)
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We report on third-harmonic generation (THG) in materials using femtosecond pulses and Z-scan method. Here we have played with beam focusing parameters and, in this way, we could track the THG signal at function of Rayleigh ranges. We observed that the femtosecond pulse has broadband spectrum and such property also affects the third harmonic (TH) spectrum. In this experiment we were able to distinguish the contribution of bulk and interface on the THG by measuring the intensity and spectral profile of the TH signal.

In vivo harmonic generation biopsy of human skin

Paper 7937-56 of Conference 7937
Date: Wednesday, 26 January 2011
Time: 9:30 AM – 9:55 AM

Author(s): Chi-Kuang Sun, National Taiwan Univ. (Taiwan) and Academia Sinica (Taiwan)
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Higher harmonic-generations, including second-harmonic-generation and third-harmonic-generation, leave no energy deposition to the interacted matters, providing the "noninvasiveness" nature desirable for clinical studies. Combined with their nonlinearity, harmonic-generation microscopy provides 3D sectioning capability. By developing the femtosecond Cr:forsterite lasers working in the high penetration window, we have recently developed a in vivo harmonic generation biopsy system with submicron 3D resolution and high penetration. In this presentation, we report our recent result on clinical trials regarding the harmonic generation biopsy of human skin. Detailed histopathological information can be obtained without removing the tissue, indicating the high potential of the developed technique.

Inactivation of encephalomyocarditis virus and herpes simplex virus by using a visible femtosecond laser

Paper 7895-28 of Conference 7895
Date: Wednesday, 26 January 2011
Time: 12:10 PM – 12:30 PM

Author(s): Shaw-Wei D. Tsen, Washington Univ. in St. Louis (United States); Kong-Thon Tsen, Arizona State Univ. (United States)
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Recently, a variety of viral systems, including M13 bacteriophage, tobacco mosaic virus (TMV), human papillomavirus (HPV) and human immunodeficiency virus (HIV) have been shown to be inactivated by the irradiation of a near-infrared subpicosecond fiber laser. These experimental results indicated that the inactivation of viruses by an ultrashort pulsed laser might involve disruption of their protein coat through laser-induced excitation of large-amplitude acoustic vibrations. In this work, we report experimental results on the inactivation of both encephalomyocarditis virus (EMCV) and herpes simplex virus (HSV) by using a visible femtosecond laser derived from the second harmonic generation of a cw mode-locked Ti-sapphire laser system. The inactivation of these viral particles has been demonstrated to depend on the laser exposure time as well as laser power density. Possible mechanisms for the inactivation will be discussed.

Helical ionizing channels generated with ultrafast interfering Bessel laser pulses

Paper 7950-11 of Conference 7950
Date: Wednesday, 26 January 2011
Time: 2:40 PM – 3:00 PM

Author(s): Nicholas Barbieri, Matthew Weidman, Matthieu Baudelet, Martin Richardson, Demetrios Christodoulides, Georgios Siviloglou, CREOL, The College of Optics and Photonics, Univ. of Central Florida (United States); Eric Johnson, Zachary Roth, The Univ. of North Carolina at Charlotte (United States)
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Using linear diffraction techniques, helical beams, which feature irradiance peaks which rotate about the optical axis with propagation, can be formed through the superposition of to oppositely charged order 1 Bessel beams. Such techniques can be extended to shape and control the propagation ultrafast laser pulses, which have sufficient irradiance to ionize air and induce laser plasma filamentation, enabling the generation of shaped ionized channels. By generating a helical beam geometry with a 12mJ femtosecond laser, ionized helical channels have been obtained in the laboratory.

Femtosecond laser-ultrasonic investigation of plasmonic fields on embedded interface

Paper 7946-70 of Conference 7946
Date: Wednesday, 26 January 2011
Time: 6:00 PM

Author(s): Hung-Pin Chen, Yu-Chieh Wen, Cheng-Hua Tsai, National Taiwan Univ. (Taiwan); Kuang-Li Lee, Pei-Kuen Wei, Academia Sinica (Taiwan); Jinn-Kong Sheu, National Cheng Kung Univ. (Taiwan); Chi-Kuang Sun, National Taiwan Univ. (Taiwan) and Academia Sinica (Taiwan)
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We demonstrate a new approach to observe the surface plasmon field on the embedded interface by using femtosecond laser ultrasonics. By analyzing the shape and temporal response of thus induced acousto-optical signals, our femtosecond laser-ultrasonic study directly reveals the plasmonic field distribution optically excited on the embedded metal/GaN interface for the first time. In this presentation, we will not only present the physical mechanisms on how to observe the plasmonic fields excited on the embedded interface through laser ultrasonics, but also compare the experimental finding with the numerical simulations.

Generation of femtosecond asymmetric beam with helical geometry

Paper 7937-70 of Conference 7937
Date: Wednesday, 26 January 2011
Time: 6:00 PM

Author(s): Chris Ceroici, Abdulhakem Y. Elezzabi, Univ. of Alberta (Canada)
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We investigate the possibility of generating a femtosecond beam with a helical wavefront and an asymmetric intensity distribution along the x-y plane by combining a radial polarization and a left or right handed circular polarization. Polarization electric field vectors, and the resulting poynting vectors, combine constructively on one quadrant and destructively on the opposite quadrant. The position of the axis of the asymmetry is dependent on the phase difference between the two beams. We then investigate the helical nature of this polarization by introducing a slanted wavefront between the two beams, and also interfering with a third linearly polarized beam with a spherical wavefront. This polarization has interesting applications in particle trapping and quantum computing since the location of the maximum intensity of the beam can be manipulated simply by adjusting the phase difference between the two input beams.

Ultrafast nonlinear optical properties and excited state dynamics of phthalocyanine thin films

Paper 7935-44 of Conference 7935
Date: Wednesday, 26 January 2011
Time: 6:00 PM

Author(s): Soma Venugopal Rao, Shuvan Prashant Turaga, P. T. Anusha, Swain Debasis, Surya Prakash Tewari, Univ. of Hyderabad (India)
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Phthalocyanines and their metal derivatives possess interesting nonlinear optical properties and find extensive applications in photonic devices such as optical limiters and all-optical switches. For practical applications these materials need to be doped in a suitable matrix. Herein we present our results on the nonlinear optical properties of alkyl and alkoxy phthalocyanine thin films studied using ~2 picosecond and ~40 femtosecond pulses. The nonlinearities were studied using Z-scan technique and the excited state dynamics using the degenerate four wave mixing and pump-probe techniques. A strong nonlinear absorption was observed with both picosecond and femtosecond pulses.

Graphene mode locked ultrafast fiber lasers

Paper 7914-53 of Conference 7914
Date: Thursday, 27 January 2011
Time: 9:30 AM – 10:00 AM

Author(s): Dingyuan Tang, Han Zhang, Nanyang Technological Univ. (Singapore); Qiaoliang Bao, Kian Ping Loh, National Univ. of Singapore (Singapore)
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We show experimentally that graphene possesses ultrafast saturable absorption, which can be used for mode locking of fiber lasers. Either the pristine graphene or graphene-polymer nanocomposite was used for mode locking erbium-doped fiber lasers. It was found that stable mode locked pulses could always be obtained, and the mode locked pulses could have much larger energy than those obtained with SESAM or CNT mode locking techniques. A unique property of graphene saturable absorption is its wavelength independence. Taking advantage of the property we have achieved wide range (~ 30nm) wavelength tunable soliton operation in erbium-doped fiber lasers. In addition, a graphene mode locked Yb-doped fiber laser operating at 1.06 micrometer was also demonstrated.

High aspect ratio taper-free micro and nano-channel fabrication in glass with ultrafast nondiffracting Bessel beams

Paper 7921-18 of Conference 7921
Date: Thursday, 27 January 2011
Time: 10:30 AM – 11:00 AM

Author(s): Manoj K. Bhuyan, Francois Courvoisier, Maxime Jacquot, Pierre-Ambroise Lacourt, Roland Salut, Luca Furfaro, John M. Dudley, Univ. de Franche-Comté (France)
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We review our recent results on femtosecond laser processing of micro and nano-channels in glass with nondiffracting Bessel beams. We show that these beams allow for an in-depth control of energy deposition, contrary to Gaussian beams. In the multishot regime, taper-free microchannels with aspect ratio up to 40 can be processed without beam translation. In the single shot regime, we demonstrate the processing of terminated nanochannels and through-channels with aspect ratio up to 100 with diameters in the range 200-800 nm. We interpret our results in terms of stationarity of the nonlinear Bessel beam propagation at ablation-level intensities.

Nanoprocessing of glass and PMMA by means of near infrared sub-15 femtosecond laser pulses

Paper 7921-19 of Conference 7921
Date: Thursday, 27 January 2011
Time: 11:00 AM – 11:20 AM

Author(s): Huijing Zhang, Karsten König, Maziar Afshar, Dara Feili, Helmut Seidel, Univ. des Saarlandes (Germany)
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A near infrared sub-15 femtosecond laser scanning microscope was employed for structuring of colored glass and PMMA. The 400 mW Ti-Sapphire laser works at 85 MHz with an M-shaped emission spectrum with maxima at 770 nm and 827 nm. By using a high NA objective, light intensity of about 10 TW/cm² at the focal plane can be reached. A mean power of less than 17 mW, which corresponds to the pulse energy of 0.2 nJ, was sufficient for drilling holes and ablating materials. Two-photon fluorescence measurements, which can be performed with the same microscope, reveal the creation of filaments within the specimens, likely caused by self focusing effects. Holes with a diameter of less than 170 nm, were produced without chemical etching. The results are compared with those obtained by using 300 fs and 3 ps laser pulses.

Femtosecond laser micro/nano patterning of biological materials

Paper 7925-5 of Conference 7925
Date: Sunday, 23 January 2011
Time: 10:50 AM – 11:20 AM

Author(s): Costas P. Grigoropoulos, Hojeong Jeon, Univ. of California, Berkeley (United States); Hirofumi Hidai, Univ. of California, Berkeley (Japan); David J. Hwang, Univ. of California, Berkeley (United States)
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This talk aims at presenting recent work at the Laser Thermal Laboratory on the microscopic and nanoscale laser modification of biological materials using ultrafast laser pulses. We have devised a new method for fabricating high aspect ratio patterns of varying height by using two-photon polymerization process in order to study contact guidance and directed growth of biological cells. Studies using NIH-3T3 and MDCK cells indicate that cell morphology on fiber scaffolds is influenced by the pattern of actin microfilament bundles. Cells experienced different strength of contact guidance depending on the ridge height. Cell morphology and motility was investigated on micronscale anisotropic cross patterns and parallel line patterns having different aspect ratios. A significant effect on cell alignment and directionality of migration was observed. Cell morphology and motility were influenced by the aspect ratio of the cross pattern, the grid size, and the ridge height. Cell contractility was examined microscopically in order to measure contractile forces generated by individual cells on self-standing fiber scaffolds. We have also introduced a method for generating user-defined nanopatterns of cell adhesion ligands by ablating an ultrathin protein adsorption resistant poly(ethylene glycol) brush layer using focused femtosecond laser pulses to expose an underlying adhesive substrate. The ablated regions were modified with peptides designed to engage with specific receptors. We were able to generate nanometer scale regions of cell adhesive peptides, while independently controlling feature size and spacing, hence allowing direct specification of the number and area of focal adhesion patterns. We have also conducted experiments to determine the effect of laser-induced nanoscale laser topography on cell adhesion.

New femtosecond sources for laser surgery of the anterior segment of the eye

Paper 7925-8 of Conference 7925
Date: Sunday, 23 January 2011
Time: 12:00 PM – 12:20 PM

Author(s): Florent Deloison, Caroline Crotti, Tal Marciano, Donald A. Peyrot, Laura Kowalczuk, Ecole Nationale Supérieure de Techniques Avancées (France); Michèle Savoldelli, Jean-Marc Legeais, Hopital Hotel Dieu (France); Karsten Plamann, Ecole Nationale Supérieure de Techniques Avancées (France)
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Femtosecond laser surgery of the anterior segment of the eye is limited in depth for cuts in oedematous cornea and sclera because of optical scattering. This phenomenon is greatly reduced by an appropriate choice of the wavelength. For our experiments and for possible clinical use we have developed a new source which consists of a diode-pumped solid-state laser emitting at 1030 nm pumping a periodically poled crystal in the configuration of a compact, robust and efficient single pass Optical Parametric Generator (OPG) not requiring a seed signal. Ex vivo surgical experiments show that 1650 nm is an optimum wavelength.

Towards high-throughput automated targeted femtosecond laser based transfection of adherent cells

Paper 7925-10 of Conference 7925
Date: Sunday, 23 January 2011
Time: 1:40 PM – 2:00 PM

Author(s): Maciej K. Antkowiak, Maria Leilani Y. Torres-Mapa, Frank J. Gunn-Moore, Kishan Dholakia, Univ. of St. Andrews (United Kingdom)
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We present two systems capable of enhanced targeted optoinjection and phototransfection of adherent mammalian cells with a femtosecond laser. We demonstrate the advantages of a spatial light modulator (SLM) for precise three dimensional positioning of the beam, which enables the implementation of a "point-and-shoot" system. It also alleviates the problem of exact beam positioning on the cell membrane by irradiation in multiple axial positions. We also present a system that uses a fast piezo mirror in combination with a Bessel beam which offers faster beam switching and larger irradiation area. Finally, we discuss imaging modalities that can be used for automated unassisted cell targeting.

Basic mechanisms of the femtosecond laser interaction with a plasmonic nanostructure in water

Paper 7925-15 of Conference 7925
Date: Sunday, 23 January 2011
Time: 3:50 PM – 4:10 PM

Author(s): Michel Meunier, Étienne Boulais, Rémi Lachaine, Charles-André Caron, Ecole Polytechnique de Montréal (Canada)
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The irradiation of a plasmonic nanostructure embedded in a biological media by a femtosecond laser could results in a highly localized plasma and heat production yielding to the generation of cavitation bubbles and nanosurgery of cells. To understand the basic mechanisms underlying this process, a combination of simulation work and experimental measurement is used to study the formation of cavitation bubbles and the generation of strong pressure waves in the medium following the irradiation of plasmonic nanostructures in a water solution. Influence of laser parameters such as pulse duration, wavelength and fluence is discussed.


Damaging cancer cells using gold nanoparticles and femtosecond pulses

Paper 7911-20 of Conference 7911
Date: Sunday, 23 January 2011
Time: 4:50 PM – 5:10 PM

Author(s): Limor Minai, Lior Golan, Gili Bisker, Dvir Yelin, Technion-Israel Institute of Technology (Israel)
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Illuminated by intense laser light at their resonance wavelength, gold nanoparticles significantly absorb and enhance the optical fields at their vicinity, producing a variety of phenomena which could be recruited to manipulate cells and tissues. In the presented work we induce damage to cells which were co-cultured with gold nanospheres and resonantly illuminated by a few high intensity femtosecond pulses at the visible part of the spectrum. We found that up to ten pulses at resonance wavelength initiated apoptosis in human fibroblasts, while larger numbers of pulses were required to induce apoptosis in cancer cells.

Femtosecond filamentation induced micro and nano-restructuring in the bulk of dielectrics and polymers

Paper 7925-23 of Conference 7925
Date: Monday, 24 January 2011
Time: 10:40 AM – 11:10 AM

Author(s): Stelios Tzortzakis, Daryoush Abdollahpour, Dimitris G. Papazoglou, Savas K. Georgiou, Foundation for Research and Technology-Hellas (Greece)
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We present results of our recent experimental studies on the physics that lead to the formation of the permanent restructuring in fused silica after the irradiation using intense femtosecond laser beams (filaments). We will also discuss the physico-chemical reactions induced in corresponding experiments in polymers (PMMA). In these studies we employ a powerful time and spectrally resolved in-line holographic technique to monitor the temporal material evolution from the initial excitation through its successive relaxation stages and up to the final permanent amorphous lattice state.

Generation of superfine structure smaller than 10 nm by interfering femtosecond laser processing

Paper 7920-10 of Conference 7920
Date: Monday, 24 January 2011
Time: 2:00 PM – 2:30 PM

Author(s): Yoshiki Nakata, Kazuma Momoo, Takuya Hiromoto, Noriaki Miyanaga, Osaka Univ. (Japan)
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When an opaque thin film is irradiated by an interfering femtosecond laser, energy is induced periodically according to the interference pattern. Each spot inflates, flows and shrinks according to the nature of the solute thin film, then it freeze due to temperature fall. The shapes of the structures are bump, spike, waterdrop. Some structures are smaller than 10 nm in curvature radius, and the aspect ratio is over 20. In addition, by changing the phase shift and power ratio between the interfering beams, duplicated structures of two shapes, or complicated structures can be generated in a single shot.

Imaging luminal atherosclerosis by femtosecond CARS to determine plaque burden

Paper 7903-40 of Conference 7903
Date: Monday, 24 January 2011
Time: 2:33 PM – 2:45 PM

Author(s): Leila B. Mostaço-Guidolin, Andrew Ridsdale, Michael S. D. Smith, Mark Hewko, Adrian F. Pegoraro, Elicia M. Kohlenberg, Bernhard J. Schattka, National Research Council Canada (Canada); Masashi Shiomi, Kobe Univ. School of Medicine (Japan); Albert Stolow, Michael G. Sowa, Alex C. T. Ko, National Research Council Canada (Canada)
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Atherosclerosis imaging was successfully demonstrated by multimodal femtosecond CARS. This study showed the power of label-free CARS imaging in differentiating plaques from healthy arterial surfaces, also demonstrated potential to interrogate atherosclerotic plaque burden associated with the types of lesion. In this study, ex vivo luminal imaging was performed to visualize morphological changes of extra-cellular proteins and lipid-rich structures within intact aortic tissue obtained from myocardial infarction-prone rabbits. Based on imaging data obtained on arterial tissues harvested from rabbits at different ages, a signal intensity-based parameter for differentiating atherosclerotic plaque burden was developed. Such parameter showed correlation with plaque burden represented by rabbit's age.

Single-polarization all-solid photonic bandgap fiber incorporating point-by-point Bragg gratings

Paper 7914-15 of Conference 7914
Date: Monday, 24 January 2011
Time: 3:30 PM – 3:50 PM

Author(s): Ryuichiro Goto, Stuart D. Jackson, The Univ. of Sydney (Australia); Robert J. Williams, Nemanja Jovanovic, Graham Marshall, Michael J. Withford, Macquarie Univ. (Australia)
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We demonstrate Point-by-Point (PbP) fiber Bragg grating inscription into the core of a single-polarization all-solid photonic bandgap (PBG) fiber using femtosecond laser pulses. The writing method does not require photosensitivity and a 20-mm-long third-order PbP Bragg grating was written into the non photosensitive, pure silica core of the PBG fiber. The grating strength was 7.5 dB (>80% reflection) at 1064 nm. The 3-dB bandwidth of the reflection was less than 200 pm. A 90-mm-diameter single-turn coiling of the fiber produced a large polarization dependent loss at 1064 nm due to the single-polarization guidance in the fiber, realizing linearly-polarized reflection.

Femtosecond laser processing of fused silica substrates for molding of polymeric materials

Paper 7925-47 of Conference 7925
Date: Monday, 24 January 2011
Time: 3:50 PM – 4:10 PM

Author(s): Marco Matteucci, Frederic Madani-Grasset, Yves Bellouard, Technische Univ. Eindhoven (Netherlands)
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In recent years patterning of glass substrates by means of combined femtosecond laser exposure under the ablation threshold and wet etching has gained considerable interest. Glass materials such as fused silica combine very interesting chemical, mechanical and optical properties for the fabrication of microstructures. To produce large numbers of low-cost micro-parts, plastic molding is considered the most promising micro-fabrication techniques. Micro molding can be used for the fabrication of elements such as active or passive components in MEMS devices, hydrophobic surfaces, cell-growth scaffolds or arrays of microlenses. We here propose to combine the nonlinear energy deposition provided by femtosecond lasers and wet etching to fabricate molds for the replica of polymer microstructures. To illustrate the use of femtosecond micromachined molds, we here demonstrate the fabrication of an array of large aspect ratio PDMS pillars. A method to enhance the de-molding of structures made in Polydimethylsiloxane (PDMS) and based on the deposition on the mold of a release coating will also be presented.

All-fiber single-mode PM thulium fiber lasers using femtosecond laser written fiber Bragg gratings

Paper 7914-17 of Conference 7914
Date: Monday, 24 January 2011
Time: 4:10 PM – 4:30 PM

Author(s): Christina Willis, Robert A. Sims, Lawrence Shah, Martin C. Richardson, CREOL, The College of Optics and Photonics, Univ. of Central Florida (United States); Jens Thomas, Rita Becker, Christian Voigtländer, Friedrich-Schiller-Univ. Jena (Germany); Andreas Tünnermann, Stefan Nolte, Friedrich-Schiller-Univ. Jena (Germany) and Fraunhofer Institute for Applied Optics and Precision Engineering (Germany)
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Two continuous wave Tm fiber lasers, at 1959 nm and 2055 nm respectively, were implemented using single mode PM silica fiber and femtosecond written fiber Bragg gratings (FBG). The laser cavity consisted of a 790 nm diode spliced to a highly reflective FBG and 2 m of active fiber. The laser output coupler was either the Fresnel reflection from the flat cleaved output fiber facet or a low reflectivity FBG. The best performance was achieved with the 1959 nm HR-LR FBG cavity, which yielded up to 5 W with 47.5% slope efficiency and 0.5 nm spectral width.

Femtosecond laser doping of TiO2 for photocatalysis

Paper 7920-16 of Conference 7920
Date: Monday, 24 January 2011
Time: 4:50 PM – 5:10 PM

Author(s): Katherine C. Phillips, Meng-Ju Sher, Anne Co, Elizabeth C. Landis, Cynthia M. Friend, Eric D. Mazur, Harvard Univ. (United States)
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We present a novel method for femtosecond-laser doping of titanium dioxide (TiO2) to shift the bandgap. TiO2 most strongly absorbs in the UV range. However, doping with metals and nitrogen has been shown to create intermediate states in the bandgap, generating a new material for visible-light photocatalysis. Using femtosecond-laser doping techniques on bulk TiO2 in a gaseous environment, we produce laser-induced periodic surface structures. We compare how the surface morphology and optical properties vary with gas composition and laser parameters. Our research presents an innovative approach to alter the structure of the TiO2 crystal for solar harvesting.

High-average power second harmonic generation of femtosecond fiber lasers

Paper 7914-27 of Conference 7914
Date: Tuesday, 25 January 2011
Time: 10:20 AM – 10:40 AM

Author(s): Steffen Hädrich, Jan Rothhardt, Tino Eidam, Thomas Gottschall, Jens Limpert, Friedrich-Schiller-Univ. Jena (Germany); Andreas Tünnermann, Friedrich-Schiller-Univ. Jena (Germany) and Fraunhofer Insitute for Applied Optics and Precision Engineering (Germany)
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Second harmonic generation of a high average power, high energy femtosecond Yb doped fiber chirped pulse amplifier is presented at various repetition. After two pre-amplification stages an 80 cm long rod-type PCF with a core diameter of 100 ตm is used to extract 70 ตJ. Compression yields 450 fs, 50 ตJ pulses. Second harmonic generation is achieved in a 500 ตm thick BBO crystals. The conversion efficiency of the second harmonic generation remained almost constant at ~50 % for all repetition rates and average power levels. At 4.08 MHz the highest average power of 129 W at 520 nm was achieved.

A femtosecond laser inscribed biochip for stem cell therapeutic applications

Paper 7929-22 of Conference 7929
Date: Tuesday, 25 January 2011
Time: 12:10 PM – 12:30 PM

Author(s): Debaditya Choudhury, William T. Ramsay, Nicholas D. Psaila, Graeme Brown, Stephen Beecher, Lynn Paterson, Ajoy K. Kar, Robert Kiss, Nicholas A. Willoughby, Heriot-Watt Univ. (United Kingdom); Steve Pells, The Univ. of Edinburgh (United Kingdom)
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For over 30 years, the extraordinary regenerative and replenishing properties of stem cells have been utilised in cancer research. Although promising advances have been made in the field, a complete clinical outcome remains elusive. A fundamental impediment involves therapeutic use of human embryonic stem cells, which is accompanied by a significant risk of cancer progression if the therapeutic implant is not entirely free of stem cells. We report on the realisation of a femtosecond laser inscribed biochip in fused silica that segregates human embryonic stem cells from their differentiated progeny based on the dissimilarity in cytoskeletal elasticity of the cells.

Femtosecond surface emitting lasers

Paper 7919-34 of Conference 7919
Date: Tuesday, 25 January 2011
Time: 3:30 PM – 4:00 PM

Author(s): Anne C. Tropper, Univ. of Southampton (United Kingdom)
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It has recently been shown that surface-emitting quantum well lasers are capable of generating sub-100-fs near-transform-limited optical pulses in self-starting passive mode-locking. The duration of these pulses is comparable with the carrier-carrier scattering time, and the laser behaviour is therefore controlled by the intrinsic dynamics of the gain structure. The presentation will review the conditions under which lasers access this regime, and describe the multiple pulsing and harmonic mode-locking phenomena that occur. An inhomogeneous two-level atom model of the semiconductor saturable absorber mirror gives insight into the role played by carrier-carrier scattering in stabilising low energy ultrashort pulses.

FROG measurements of a femtosecond modelocked VECSEL

Paper 7919-37 of Conference 7919
Date: Tuesday, 25 January 2011
Time: 4:45 PM – 5:00 PM

Author(s): Stephen P. Elsmere, Keith G. Wilcox, Adrian H. Quarterman, Zakaria Mihoubi, Anne C. Tropper, Univ. of Southampton (United Kingdom)
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Whilst many reported femtosecond VECSELs produce near transform limited pulses, VECSELs can operate in regimes where pulses up to twice the transform limit are obtained. Here we report on measurements performed using second harmonic frequency resolved optical gating (SH-FROG) to investigate the phase structure of chirped pulses with durations between 500 and 750 fs, at repetition rates from 1 to 6 GHz. We also investigate the pulse quality when multiple pulses are circulating intracavity and find that no significant pulse degradation occurs, highlighting the potential of producing high quality pulse trains at high repetition rates using harmonically modelocked VECSELs.

High peak power femtosecond pulse VECSELs for terahertz time domain spectroscopy

Paper 7919-38 of Conference 7919
Date: Tuesday, 25 January 2011
Time: 5:00 PM – 5:15 PM

Author(s): Keith G. Wilcox, Aaron L. Chung, Adrian H. Quarterman, Zakaria Mihoubi, Univ. of Southampton (United Kingdom); Ian Farrer, Harvey E. Beere, David A. Ritchie, Univ. of Cambridge (United Kingdom); Vasilis Apostolopoulos, Anne C. Tropper, Univ. of Southampton (United Kingdom)
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We report on a high peak power femtosecond modelocked VECSEL and its application as a driving laser for an all-semiconductor terahertz-time-domain spectrometer. The VECSEL produced near-transform-limited 335 fs sech2 pulses at a fundamental repetition rate of 1 GHz, a centre wavelength of 999 nm and an average output power of 120 mW. We report on the effect that this high peak power and short pulse duration has on our generated THz signal, where an increase in the THz power and bandwidth is observed.

Towards all-in-glass micro-actuators fabricated with femtosecond lasers

Paper 7925-45 of Conference 7925
Date: Tuesday, 25 January 2011
Time: 5:00 PM – 5:20 PM

Author(s): Yves Bellouard, Technische Univ. Eindhoven (Netherlands); Ali A. Said, Mark A. Dugan, Philippe Bado, Translume, Inc. (United States)
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Femtosecond lasers exposure combined with a chemical etching step have been recently demonstrated as an efficient and versatile process for manufacturing complex three-dimensional structures in glass materials. This new fabrication method is particularly interesting for MEMS and in particular for monolithic structures that embed multiple functions, like waveguides, channels and mechanical elements. Recently, we demonstrated that, and although it may sound counterintuitive, fused silica has excellent mechanical properties. Furthermore, we showed that flexures manufactured using this process can withstand very high stress and large deflection. As a proof-of-concept, an all-in glass monolithic micro-displacement sensor combining waveguides and a double compound linear guidance was made. Here, we present a step towards fully integrated MEMS devices. In addition to the mechanical guidance and the sensing, we report on a scheme to introduce actuating functions to the device in which a set of electrodes embedded in the structure are used to drive the mechanism. In this paper, we describe the fabrication process and the performances of a first prototype of a femtosecond laser-manufactured actuator.

Towards all-in-glass micro-actuators fabricated with femtosecond lasers

Paper 7920-45 of Conference 7920
Date: Tuesday, 25 January 2011
Time: 5:00 PM – 5:20 PM

Author(s): Yves Bellouard, Technische Univ. Eindhoven (Netherlands); Ali A. Said, Mark A. Dugan, Philippe Bado, Translume, Inc. (United States)
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Femtosecond lasers exposure combined with a chemical etching step have been recently demonstrated as an efficient and versatile process for manufacturing complex three-dimensional structures in glass materials. This new fabrication method is particularly interesting for MEMS and in particular for monolithic structures that embed multiple functions, like waveguides, channels and mechanical elements. Recently, we demonstrated that, and although it may sound counterintuitive, fused silica has excellent mechanical properties. Furthermore, we showed that flexures manufactured using this process can withstand very high stress and large deflection. As a proof-of-concept, an all-in glass monolithic micro-displacement sensor combining waveguides and a double compound linear guidance was made. Here, we present a step towards fully integrated MEMS devices. In addition to the mechanical guidance and the sensing, we report on a scheme to introduce actuating functions to the device in which a set of electrodes embedded in the structure are used to drive the mechanism. In this paper, we describe the fabrication process and the performances of a first prototype of a femtosecond laser-manufactured actuator.

Efficient spherical wavefront correction near the focus of the petawatt-level femtosecond CPA laser system

Paper 7916-36 of Conference 7916
Date: Tuesday, 25 January 2011
Time: 6:00 PM

Author(s): Zhijun Ren, Xiaoyan Liang, Lianghong Yu, Xiaoming Lu, Ruxin Li, Zhizhan Xu, Shanghai Institute of Optics and Fine Mechanics (China)
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By directly measuring the spherical wavefront near the focus, we demonstrated a approach to efficiently correct convergent spherical wavefront by installing a common small aperture deformable mirror (DM) in the middle of 0.89PW/29.0fs Ti:sapphire CPA laser chain. It is, to our knowledge, the first time attain the near perfect correction result in ultra-intensity laser system by correcting convergent spherical wavefront using a small aperture DM in adaptive optical loop. Finally the maximum peak intensity of 2.36×10^21 W/cm2 was obtained with an f/4 off-axis parabola at the output power of 0.89 PW.

Generation of complicated or duplicated structure by interfering femtosecond laser processing of metallic thin film

Paper 7920-41 of Conference 7920
Date: Tuesday, 25 January 2011
Time: 6:00 PM

Author(s): Takuya Hiromoto, Kazuma Momoo, Yoshiki Nakata, Noriaki Miyanaga, Osaka Univ. (Japan)
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Interference ultra-short pulse laser processing can make nano-structures on metallic thin films. The unit nano-structures are nano-waterdrop, nanocrown, nanobump etc.. They change according to the character of target, and distribution of them is periodic according to the interference pattern. An interference pattern of four beams, diffracted by a transmission grating, is like a matrix. We generated arranged periodic structures different from the past experiments, by changing the configuration of four 1st beams. Parameters of an interference pattern are wavelength, correlation angle, intensity and phase shift distributions between the beams. To generate complicated or duplicated structures, intensity and phase shift distributions are important.

Microwelding of glass substrates by double pulse irradiation of femtosecond laser

Paper 7920-50 of Conference 7920
Date: Tuesday, 25 January 2011
Time: 6:00 PM

Author(s): Makoto Iida, RIKEN (Japan) and Tokyo Denki Univ. (Japan); Yasutaka Hanada, Koji Sugioka, RIKEN (Japan); Hiroshi Takai, Tokyo Denki Univ. (Japan); Katsumi Midorikawa, RIKEN (Japan)
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In this paper, we propose to use the double-pulse irradiation method with femtosecond laser for glass welding to improve both welding quality and efficiency. In the experiment, we irradiate double-pulse of femtosecond laser to the interface of stacked two glass substrates with a repetition rate of 200 kHz. The delay time of the two pulses is changed from 100 fs to around 2 ps. Efficient welding of glass can be achieved by double-pulse irradiation with the delay time of sub ps, since the avalanche ionization should occur within a couple of ps after the last pulse irradiation.

Multiphoton lithography and ITO structuring by high repetition-rate sub-15 femtosecond laser pulses

Paper 7920-43 of Conference 7920
Date: Tuesday, 25 January 2011
Time: 6:00 PM

Author(s): Maziar Afshar, Somaie Saremi, Henning Völlm, Dara Feili, Helmut Seidel, Martin H. Straub, Huijing Zhang, Karsten König, Univ. des Saarlandes (Germany)
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We report on experiments using a near-infrared Ti:Sapphire laser system based on a 85 MHz, sub-15 fs resonator. In the negative photoresist SU-8 multiphoton polymerization of 3D structures resulted in a minimum line width of approximately 80 nm at aspect ratios in excess of 100:1. The second part of our contribution deals with sub-wavelength nanostructuring and laser-annealing of thin indium-tin-oxide (ITO) films. The ablation experiments allowed for the generation of cuts of 80 nm in width. For comparison, both our experiments on polymer and ITO were carried out at different pulse widths of up to 2.7 ps. The dependence of cuts on scan parameters as well as ITO film properties such as oxygen content was also investigated.

Non-destructive analysis on femtosecond laser doped silicon

Paper 7920-44 of Conference 7920
Date: Tuesday, 25 January 2011
Time: 6:00 PM

Author(s): Yu-Ting Lin, Harvard Univ. (United States); Matthew J. Smith, Silvija Gradecak, Massachusetts Institute of Technology (United States); Eric D. Mazur, Harvard Univ. (United States)
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Silicon doped with Chalcogens using femtosecond laser pulses can achieve a high doping concentration (~1 %) and unique properties. This material exhibits near-unity absorption extending from the visible to the mid-infrared and metallic-like conduction. Thus, it is a potential candidate for advanced optoelectronic devices. To further understand this material, we utilize non-destructive optical tools including Raman spectroscopy and FTIR to characterize laser-induced changes in crystallinity, dopant profiles, and optical properties at various processing parameters. Our findings contribute to a better understanding of the structural and optical characteristics, completing a picture of the silicon surface condition after femtosecond laser irradiation.

Optical device fabrication using femtosecond laser processing with glass-hologram

Paper 7925-44 of Conference 7925
Date: Tuesday, 25 January 2011
Time: 6:00 PM

Author(s): Jun'ichi Suzuki, Yasunori Arima, Shuhei Tanaka, New Glass Forum (Japan)
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Femtosecond laser processing with glass-hologram is an efficient processing method that an arbitrary three-dimensional intensity distribution produced by the glass-hologram is patterned into transparent materials at one laser shot. It has higher productivity of optical devices with higher accuracy. A glass-hologram is one of the key elements. Its phase distribution is obtained using computer-generated holography. Then the phase distribution is transferred on a glass surface with electron beam lithography and reactive ion etching. In this work, we report on optical devices fabricated by femtosecond laser processing with glass-hologram. We also investigate relation between characteristic of the optical device and the glass-hologram parameters or performance.

Scattering-controlled femtosecond-laser induced nanostructuring of TiO2 thin films

Paper 7925-42 of Conference 7925
Date: Tuesday, 25 January 2011
Time: 6:00 PM

Author(s): Susanta K. Das, Arkadi Rosenfeld, Martin Bock, Max-Born-Institut für Nichtlineare Optik und Kurzzeitspektroskopie (Germany); Andreas Pfuch, Innovent e.V. (Germany); Wolfgang Seeber, Friedrich-Schiller-Univ. Jena (Germany); Rüdiger Grunwald, Max-Born-Institut für Nichtlineare Optik und Kurzzeitspektroskopie (Germany)
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Laser-induced periodic nanostructuring of TiO2 thin films was investigated in comparison to bulk material. The mechanism was found to be strongly influenced by surface morphology and optical quality of the layer. At a pulse duration of 150 fs and a center wavelength of 800 nm, the formation of high spatial frequency ripples with periods of 150 nm was observed even at low pulse numbers in the range of N= 5 if the process was favoured by a sufficiently high density of scattering centers. It is concluded that a more subtle control of scattering should enable for an improved structuring performance.

Numerical modelling of optical Stark effect saturable absorbers in mode-locked femtosecond VECSELs

Paper 7919-26 of Conference 7919
Date: Tuesday, 25 January 2011
Time: 9:45 PM – 10:00 PM

Author(s): Adrian H. Quarterman, Geoff J. Daniell, Stewart Carswell, Keith G. Wilcox, Zakaria Mihoubi, Aaron L. Chung, Vasilis Apostolopoulos, Anne C. Tropper, Univ. of Southampton (United Kingdom)
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Passively mode-locked VECSELs have shown themselves to be capable of producing pulses as short as 60 fs, but the mechanisms behind the formation of these pulses remains poorly understood. Previous numerical models have shown that the optical Stark effect is capable of shortening pulses to sub-picosecond durations in the absence of bleaching. Here we present a more advanced numerical model of the interaction between an optical pulse and an absorbing quantum well which shows that the distortion of the exciton resonance due to the optical Stark effect can shorten pulses under realistic VECSEL operating conditions.

Mode-locking theory for ultra-short few-femtosecond laser pulses

Paper 7933-53 of Conference 7933
Date: Thursday, 27 January 2011
Time: 9:00 AM – 9:20 AM

Author(s): Jose Nathan Kutz, Univ. of Washington (United States); Edward D. Farnum, Kean Univ. (United States)
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We propose a new theoretical model that is valid for ultra-fast pulse propagation in a mode-locked laser cavity in the few femtosecond to hundreds of attoseconds pulse regime, thus deriving the equivalent of the master mode-locking equation for ultra-short pulses that has dominated mode-locking theory for two decades. The short pulse equation with dissipative gain and loss terms allows for the generation of stable ultra-short optical pulses from initial white-noise, thus providing the first theoretical framework for quantifying the pulse dynamics and stability as pulseswidths approach the attosecond regime.

Mid-infrared femtosecond frequency combs for sensing and optical clocks

Paper 7917-45 of Conference 7917
Date: Thursday, 27 January 2011
Time: 9:20 AM – 9:50 AM

Author(s): Irina T. Sorokina, Norwegian Univ. of Science and Technology (Norway); Evgeni Sorokin, Vienna Univ. of Technology (Austria)
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We review recent advances in frequency comb sources based on Cr2+:chalcogenide lasers, operating between 1.9 and 3.6 micron, and their applications to "frequency comb spectroscopy" and other sensing techniques. These lasers exhibit the broadest among existing lasers continuous tuning over 1400 nm and 80-fs pulses, all at ambient conditions. The lasers operate in transportable hybrid fiber-bulk form, and allow novel techniques like dual-comb method and intracavity spectroscopy. The femtosecond frequency combs also serve as a starting point for synchroniously pumped OPOs. The talk highlights the radical efficiency increase when such sources are applied to high-resolution molecular spectroscopy and gas sensing.

Power scaling and high-power applications of a femtosecond enhancement cavity

Paper 7914-54 of Conference 7914
Date: Thursday, 27 January 2011
Time: 10:00 AM – 10:30 AM

Author(s): Ioachim Pupeza, Max-Planck-Institut für Quantenoptik (Germany) and Ludwig-Maximilians-Univ. München (Germany); Tino Eidam, Friedrich-Schiller-Univ. Jena (Germany); Jan Kaster, Jens Rauschenberger, Max-Planck-Institut für Quantenoptik (Germany) and Ludwig-Maximilians-Univ. München (Germany); Birgitta Bernhardt, Akira Ozawa, Ernst E. Fill, Max-Planck-Institut für Quantenoptik (Germany); Vladimir Pervak, Ludwig-Maximilians-Univ. München (Germany); Alexander A. Apolonski, Max-Planck-Institut für Quantenoptik (Germany) and Ludwig-Maximilians-Univ. München (Germany); Thomas Udem, Max-Planck-Institut für Quantenoptik (Germany); Jens Limpert, Friedrich-Schiller-Univ. Jena (Germany); Zeyad A. Alahmed, Abdallah M. Azzeer, King Saud Univ. (Saudi Arabia); Andreas Tünnermann, Friedrich-Schiller-Univ. Jena (Germany); Theodor W. Hänsch, Ferenc Krausz, Max-Planck-Institut für Quantenoptik (Germany) and Ludwig-Maximilians-Univ. München (Germany)
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We discuss the power scalability of a bow-tie enhancement cavity, seeded by an Yb-based fiber CPA system. The seed laser parameters are: 78 MHz repetition frequency, 200 fs pulse duration and 50 W of maximum average power. Peak intensities exceeding 10^14 W/cm^2 at the 22 ตm-radius cavity focus (1/e^2-intensity) for several enhancement regimes with circulating powers of up to 72 kW are demonstrated. We find that the enhancement is primarily limited by intensity-dependent processes occurring in the cavity mirrors, such as third-harmonic generation and nonlinear group delay dispersion and we propose solutions to overcome these limitations. We report on our group's recent progress regarding the applications of this system.

Femtosecond laser doped silicon for photovoltaic applications

Paper 7921-40 of Conference 7921
Date: Thursday, 27 January 2011
Time: 5:20 PM – 5:35 PM

Author(s): Meng-Ju Sher, Mark T. Winkler, Yu-Ting Lin, Eric D. Mazur, Harvard Univ. (United States)
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Silicon is doped to concentrations above the metal-insulator transition threshold via femtosecond laser doping techniques creating a novel material that has potential for photovoltaic applications. By focusing femtosecond laser pulses on the surface of silicon in a sulfur hexafluoride (SF6) environment, silicon is doped with 1% atomic sulfur. This material exhibits near-unity, broadband absorption from visible to lower than 0.5 eV near infrared light, deep below the silicon bandgap. We use temperature-dependent Hall measurements to investigate electron transport as well as identify the energy states of the sulfur donors and hence the location of the intermediate band.

Femtosecond laser doped silicon for photovoltaic applications

Paper 7920-40 of Conference 7920
Date: Thursday, 27 January 2011
Time: 5:20 PM – 5:35 PM

Author(s): Meng-Ju Sher, Mark T. Winkler, Yu-Ting Lin, Eric D. Mazur, Harvard Univ. (United States)
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Silicon is doped to concentrations above the metal-insulator transition threshold via femtosecond laser doping techniques creating a novel material that has potential for photovoltaic applications. By focusing femtosecond laser pulses on the surface of silicon in a sulfur hexafluoride (SF6) environment, silicon is doped with 1% atomic sulfur. This material exhibits near-unity, broadband absorption from visible to lower than 0.5 eV near infrared light, deep below the silicon bandgap. We use temperature-dependent Hall measurements to investigate electron transport as well as identify the energy states of the sulfur donors and hence the location of the intermediate band.

Making the molecular movie: first frames (Keynote Presentation)

Paper 7937-39 of Conference 7937
Date: Tuesday, 25 January 2011
Time: 10:45 AM – 11:10 AM

Author(s): Dwayne R. J. Miller, Univ. Hamburg (Germany) and Deutsches Elektronen Synchrotron (Germany) and Univ. of Toronto (Canada)
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Femtosecond Electron Diffraction has enabled atomic resolution to structural changes as they occur, essentially watching atoms move in real time - directly observe transition states. This experiment has been referred to as "making the molecular movie" and has been previously discussed in the context of a gedanken experiment. With the recent development of femtosecond electron pulses with sufficient number density to execute single shot structure determinations, this experiment has been finally realized. A new concept in electron pulse generation was developed based on a solution to the N-body electron propagation problem involving up to 10,000 interacting electrons that has led to a new generation of extremely bright electron pulsed sources that minimizes space charge broadening effects. Previously thought intractable problems of determining t=0 and fully characterizing electron pulses on the femtosecond time scale have now been solved through the use of the laser pondermotive potential to provide a time dependent scattering source. Synchronization of electron probe and laser excitation pulses is now possible with an accuracy of 10 femtoseconds to follow even the fastest nuclear motions. The camera for the "molecular movie" is now in hand.

Near-field nanoablation thruster of gold solid nanoparticles by backside femtosecond laser irradiation for biomedical application

Paper 7925-11 of Conference 7925
Date: Sunday, 23 January 2011
Time: 2:00 PM – 2:20 PM

Author(s): Go Obara, Tomoya Miyanishi, Toshiyuki Honda, Nikolay N. Nedyalkov, Petar A. Atanasov, Mitsuhiro Terakawa, Minoru Obara, Keio Univ. (Japan)
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We present a novel method of the gold particles transfer by backside irradiation of femtosecond laser. This method is to push the SOLID phase gold nanoparticles on the substrate by nanoablation thruster underneath the particle.

Diagnosing hepatocellular carcinoma with the intensity and the lifetime of two-photon red autofluorescences

Paper 7903-105 of Conference 7903
Date: Sunday, 23 January 2011
Time: 5:30 PM

Author(s): Tzu-Ming Liu, Chien-Tai Hsieh, Yu-Shing Chen, Fu-Lien Huang, National Taiwan Univ. (Taiwan); Hsin-Yi Huang, Wen-Jeng Lee M.D., National Taiwan Univ. Hospital (Taiwan); Chun-Ta Kung, Chi-Kuang Sun, National Taiwan Univ. (Taiwan)
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We demonstrated that the intensity levels and lifetimes of two-photon autofluorescences (2PAF) in human liver tissues can be exploited to diagnose hepatocellular carcinoma (HCC). Excited by an infrared femtosecond laser, we suppressed the two-photon autofluorescences of most endogenous fluorophores and made red autofluorescences more specific to particular molecules in the cryo-sectioned human livers. We found HCC tissues have reduced levels of 2PAF and longer fluorescence lifetimes. Without a staining, the HCC tissues can thus be differentiated from non-tumor ones on the same patient(p<0.001).

Direct laser writing of nonlinear properties in photosensitive glass

Paper 7925-20 of Conference 7925
Date: Monday, 24 January 2011
Time: 9:10 AM – 9:30 AM

Author(s): Gautier Papon, Univ. Bordeaux 1 (France); Jiyeon Choi, CREOL, The College of Optics and Photonics, Univ. of Central Florida (United States); Arnaud Royon, Univ. Bordeaux 1 (France); Martin C. Richardson, Leonid B. Glebov, CREOL, The College of Optics and Photonics, Univ. of Central Florida (United States); Lionel Canioni, Univ. Bordeaux 1 (France)
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A 1030 nm pulsed femtosecond laser has been use to induce modifications in silver containing glass namely femto-photo luminescent glass (FPL) and Photo-thermo refractive glass (PTR). The interaction resulted in the creation of stable silver clusters forming below refraction-limit 3D structures. Those nano-structures exhibit non-linear properties such as SHG and THG as well as fluorescence. Due to multiphoton absorption, free electrons are created enabling the reduction of Ag+ silver ions into Ag0 and subsequently ionized Ag-clusters. The ion concentration gradient creates a buried electric field enabling non-linear properties. Influence of polarization, dose and fluence in the non-linear properties are investigated.

Time-resolved imaging of bulk a-SiO2 upon various ultrashort excitation sequences

Paper 7925-26 of Conference 7925
Date: Monday, 24 January 2011
Time: 11:50 AM – 12:10 PM

Author(s): Alexandre Mermillod-Blondin, Max-Born-Institut für Nichtlineare Optik und Kurzzeitspektroskopie (Germany); Cyril Mauclair, Lab. Hubert Curien (France); Arkadi Rosenfeld, Max-Born-Institut für Nichtlineare Optik und Kurzzeitspektroskopie (Germany); Jörn Bonse, Bundesanstalt für Materialforschung und -prüfung (Germany); Razvan I. Stoian, Eric Audouard, Lab. Hubert Curien (France)
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We present a time-resolved microscopy method that allows for tracking laser-induced refractive index changes into the bulk of transparent materials. Our setup is based on a commercially available phase-contrast microscope illuminated by a pulsed laser source in an extended pump-probe scheme. The excitation (pump) beam can be temporally manipulated with the help of a pulse shaping unit prior to tight focusing (numerical aperture of 0.45) into the transparent target. Results of the spatio-temporal dynamics obtained when irradiating a-SiO2 samples with various excitation pulse profiles (e.g. subpicosecond duration pulses, double pulse sequence) will be shown.

Ultrafast hot carrier dynamics in InN epitaxial films

Paper 7937-35 of Conference 7937
Date: Monday, 24 January 2011
Time: 4:30 PM – 4:55 PM

Author(s): Tsongru Tsai, Chih-Fu Chang, Chih-Wei Kuo, Cheng-Yu Chang, National Taiwan Ocean Univ. (Taiwan); S. Gwo, National Tsing Hua Univ. (Taiwan)
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Ultrafast hot carrier dynamics in Indium nitride (InN) epitaxial films were investigated by femtosecond time-resolved pump-probe reflectivity measurements. Carrier density and carrier energy dependence of the hot carrier dynamics in InN were studied by varying the pump laser power and wavelength, respectively. Experimental results show that the hot carrier relaxation can be fitted by a biexponential relaxation process. The fast relaxation rate increases with increasing carrier density (N), which is measured as N0.5. The fast relaxation rate also increases with increasing carrier energy (E), which is measured as E0.53. These observations reveal that the electron-electron scattering plays an important role in hot carrier relaxation. In addition, the slow relaxation is dominated by Auger scattering and the slow relaxation rate is independent of the carrier energy. The defect-related trapping time in InN was estimated to be ~515 ps.

Nanostructure formation on silicon surfaces by high repetition-rate sub-15fs near-infrared laser pulses

Paper 7920-26 of Conference 7920
Date: Tuesday, 25 January 2011
Time: 4:40 PM – 5:00 PM

Author(s): Martin H. Straub, Karsten König, Univ. des Saarlandes (Germany)
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On low-indexed crystalline silicon surfaces characteristic micro- and nanostructures are formed using high repetition-rate sub-15 fs Ti:Sapphire laser pulses. Sub-nJ pulse energies efficiently induce profound structural and compositional changes in the high-numerical aperture focus of our laser scanning microscope. For example, a Si(100) surface exposed to laser light in water revealed periodic changes in morphology involving oxide particle formation and sub-10 nm hole arrangements, whereas a similar experiment in oil resulted in nano-scale deposition of carbon compounds. We present novel investigations as well as analysis and discussion of phenomena and compare results with observations made using longer pulse widths.

Nanostructure formation on silicon surfaces by high repetition-rate sub-15fs near-infrared laser pulses

Paper 7925-26 of Conference 7925
Date: Tuesday, 25 January 2011
Time: 4:40 PM – 5:00 PM

Author(s): Martin H. Straub, Karsten König, Univ. des Saarlandes (Germany)
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On low-indexed crystalline silicon surfaces characteristic micro- and nanostructures are formed using high repetition-rate sub-15 fs Ti:Sapphire laser pulses. Sub-nJ pulse energies efficiently induce profound structural and compositional changes in the high-numerical aperture focus of our laser scanning microscope. For example, a Si(100) surface exposed to laser light in water revealed periodic changes in morphology involving oxide particle formation and sub-10 nm hole arrangements, whereas a similar experiment in oil resulted in nano-scale deposition of carbon compounds. We present novel investigations as well as analysis and discussion of phenomena and compare results with observations made using longer pulse widths.

Evaluation of a refractive index profiles for a modification induced by focused femtosecond laser irradiation in the optical glasses

Paper 7920-46 of Conference 7920
Date: Tuesday, 25 January 2011
Time: 6:00 PM

Author(s): Tomohiro Hashimoto, Shuhei Tanaka, New Glass Forum (Japan)
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We report on a refractive index modification (?n) induced by femtosecond irradiation and evaluation of the profile for created lines inside the different types of optical glasses. The ?n profiles of modification were obtained with Qualitative Phase Microscopy technique and presented systematically for a different input power and a variety of glasses. The ?n profile changed with focusing condition using 10× (N.A.=0.3) or 40× (N.A.=0.85), and input power in a single glass. These results could be useful for a design or selection of glasses for micro optics produced by femtosecond laser fabrication.

The high-power femtosecond pulses amplified by an all-fiber system based on the model of self-similar amplification

Paper 7914-101 of Conference 7914
Date: Tuesday, 25 January 2011
Time: 6:00 PM

Author(s): Tianxin Yang, Tianhe Wang, Delin Yang, Junlong Wang, Mei Sang, Tianjin Univ. (China)
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In this paper a theoretical model of self-similar amplifications is studied experimentally in an all-fiber high power amplifier. The output vs. input characteristics of this amplifier are measured when the various femtosecond pulses at different energies and different shapes are inputted. It is verified that the all-fiber high power amplifier system is indeed operating in the way of self-similar amplifications by analyzing the data of the amplified pulses along with the data of the input pulses. Finally, nearly transform-limited ultra-short pulses with high average power of 500 mW and time-bandwidth product of 0.342 are obtained by compressing the output pulses from the fiber amplifier to the ultra-short pulses of 113 fs at the center wavelength of 1552 nm using a segment of DCFs with large negative group velocity dispersion. The results demonstrated that the operating mode of the amplifier is consistent with the typical self-similar amplification model.

Ultrafast exciton and charge transfer in small aggregates of carbon nanotubes

Paper 7937-65 of Conference 7937
Date: Wednesday, 26 January 2011
Time: 3:05 PM – 3:30 PM

Author(s): Larry Lüer, Instituto Madrileño de Estudios Avanzados (Spain); Jared Crochet, Los Alamos National Lab. (United States); Tobias Hertel, Univ. of Würzburg (Germany); Sajjad Hoseinkhani, Italian Institute of Technology (Italy); Giulio Cerullo, Politecnico di Milano (Italy); Guglielmo Lanzani, Italian Institute of Technology (Italy)
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We studied excitation energy transfer in small hexagonal aggregates of carbon nanotubes by femtosecond spectroscopy with down to 7 fs pulse duration. After resonant excitation of the first excitonic transition in (6,5) tubes, we found that excitons are transferred towards (7,5) tubes within less than 10 fs. After pumping at high photon energies, favoring the formation of free carriers, we found clear spectroscopic signatures allowing us to trace ultrafast charge transfer, trapping and recombination.

Three-dimensional polymer nanostructures for applications in cell biology generated by high-repetition-rate sub-15-fs near-infrared laser pulses

Paper 7908-20 of Conference 7908
Date: Thursday, 27 January 2011
Time: 8:00 AM – 8:30 AM

Author(s): Martin H. Straub, Martin Licht, Karsten Koenig, Maziar Afshar, Dara Feili, Helmut Seidel, Univ. des Saarlandes (Germany)
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In recent years two-photon photopolymerization has emerged as a novel and extremely powerful technique of nanostructure formation. We report on the fabrication of three-dimensional cell cages made of biocompatible polymer material, which allow for cell development in a more natural environment than conventional planar growth methods. For the nanofabrication experiments a commercial high numerical-aperture microscope setup is used to focus near-infrared sub-15 fs pulsed Ti:Sapphire laser light into the polymer material. Ultimately, our research aims at specific cell cages of sophisticated architecture involving sub-100 nm features, which provide cell culture substrates far superior to those currently existing.

Evaluation of the collateral damage during a femtosecond-laser axotomy by using a multimodal microscopy workstation

Paper 7902-24 of Conference 7902
Date: Sunday, 23 January 2011
Time: 10:30 AM – 10:50 AM

Author(s): Omar E. Olarte, Susana I. C. O. Santos, Manoj Mathew, Sotiris Psilodimitrakopoulos, Pablo Loza-Alvarez, ICFO - Instituto de Ciencias Fotónicas (Spain)
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Using a femtosecond laser, it is possible to dissect individual nerve axons within living Caenorhabditis elegans. Such procedure possesses great potential for studying nerve regeneration. Furthermore, the assessment of the damage around the wound after the surgery is important because it allows understanding any possible side effect during the regeneration process. In this study we provide an approach for simultaneous axotomy and high resolution imaging: the collateral damage is assessed by visualization of anatomical references of the nearby tissues by using a set of linear and nonlinear microscopy techniques. This allows observing the effects caused in the damaged region during a nano-surgery intervention.

On the role of stress in the chemical etching of fused silica exposed to low-energy femtosecond laser pulses

Paper 7925-49 of Conference 7925
Date: Monday, 24 January 2011
Time: 4:30 PM – 4:50 PM

Author(s): Audrey Champion, Yves Bellouard, Technische Univ. Eindhoven (Netherlands)
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Recently, it was demonstrated that femtosecond lasers pulses with energies below the ablation threshold locally enhance the etching rate of fused silica: regions that are exposed to the laser beam are etched faster. This remarkable property has been exploited for fabricating a variety of micro-structures like fluidic channels, tunnels or more complex devices, like mechanical flexures. The physical effect causing the etching-rate local enhancement is still debated and various hypotheses have been proposed among which localized densification models seem to prevail. In that context, we recently demonstrated that the amount of deposited energy plays a very important role. It was found that for laser repetition rates where no cumulative effects are observed, there exists an optimal amount of energy deposited to achieve the fastest etching rate. These observations suggest that the stress introduced during laser exposure plays also an important role in the process. Our hypothesis is that not only structural changes such as the appearance of lower-order ring structures enhances the etching rate but also the stress surrounding laser-exposed regions. To further understand the role of the stress, here we report on experiments where we accurately control laser writing parameters of lines and patterns not only with respect to their spatial localizations in the specimen but also in term of deposited energy. Etching profiles observations are then compared with finite-element predictions of the stress distribution surrounding laser-patterns to estimate the magnitude of the stress-induced etching.

Laser-induced breakdown spectroscopy with tailored femtosecond pulses for 3-dimensional chemical imaging with high spatial resolution

Paper 7920-24 of Conference 7920
Date: Tuesday, 25 January 2011
Time: 3:50 PM – 4:20 PM

Author(s): Jutta Mildner, Cristian Sarpe-Tudoran, Lars Englert, Dirk Otto, Nadine Goette, Matthias Wollenhaupt, Waldemar Wessel, Angelika Brueckner-Foit, Thomas Baumert, Univ. Kassel (Germany)
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Laser-induced breakdown spectroscopy with tailored femtosecond pulses for 3-dimensional chemical imaging with high spatial resolution

Paper 7925-24 of Conference 7925
Date: Tuesday, 25 January 2011
Time: 3:50 PM – 4:20 PM

Author(s): Jutta Mildner, Cristian Sarpe-Tudoran, Lars Englert, Dirk Otto, Nadine Goette, Matthias Wollenhaupt, Waldemar Wessel, Angelika Brueckner-Foit, Thomas Baumert, Univ. Kassel (Germany)
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Dispersion controlled tellurite air-clad fibers for supercontiuum generations pumped by picosecond and femtosecond fiber lasers respectively

Paper 7934-39 of Conference 7934
Date: Wednesday, 26 January 2011
Time: 6:00 PM

Author(s): Meisong Liao, Xin Yan, Guanshi Qin, Chitrarekha B. Chaudhari, Takenobu Suzuki, Yasutake Ohishi, Toyota Technological Institute (Japan)
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Tellurite air-clad fibers with 1 ตm hexagonal core and different size of holey region were fabricated. The chromatic dispersion of these fibers can be tailored effectively by changing the diameter ratio of holey region to core. One actave flattened SC generation, pumped by a 1064 nm picosecond fiber laser with the pulse energy of several hundred pJ, was demonstrated. Effective second and third harmonic generation was obtained by a 1557 nm femtosecond fiber laser. The dependences of SC generation on the dispersion and nonlinearity were analyzed. Such fibers, with high nonlinearity and controlled dispersion are significant in nonlinear applications.

Fiber-based combined optical coherence and multiphoton microscopy

Paper 7892-9 of Conference 7892
Date: Saturday, 22 January 2011
Time: 11:30 AM – 11:50 AM

Author(s): Gangjun Liu, Zhongping Chen, Beckman Laser Institute and Medical Clinic (United States)
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This manuscript demonstrates a multimodal imaging system which combined multiphoton microscopy (MPM) imaging modality with Fourier domain (FD) optical coherence microscopy (OCM) modality. The system used a single fiber femtosecond laser as the light source for both MPM and OCM modality. The femtosecond fiber laser has a central wavlength of 1.03um and a pulse width of 120fs. The systems used fiber based devices for both MPM and OCM. The MPM and OCM shared the same excitation light path. The excitation light was delivered with the core of a dual-clad fiber. The MPM signal was collected by the clad of the dual-clad fiber. The FD OCM used a home-built InGaAs detector array spectrometer.

Holographic spatiotemporal lens (HSTL)

Paper 7925-7 of Conference 7925
Date: Sunday, 23 January 2011
Time: 11:40 AM – 12:00 PM

Author(s): Kouhei Kimura, Satoshi Hasegawa, Yoshio Hayasaki, Utsunomiya Univ. (Japan)
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We propose a holographic spatiotemporal lens (HSTL) to improve spatial resolution of two-photon excitation spot as a new focusing technique of femtosecond laser pulse. Femtosecond laser pulses dispersed by a diffraction grating or a prism-pair are irradiated to a chirped diffractive lens (CSTL) displayed on a spatial light modulator (SLM). The CDL has a spatially chirp of focal length for a design for its corresponding wavelength. The shortest pulse was experimentally obtained only at the focal plane. The pulse duration was also supported with a computer simulation. Furthermore, we demonstrated parallel spatiotemporal focusing using a multiplexed HSTL.

Ultrafast coherent optoelectronics of semiconductor-metal hybrid structures

Paper 7937-31 of Conference 7937
Date: Monday, 24 January 2011
Time: 2:20 PM – 2:45 PM

Author(s): Claudia Ruppert, Technische Univ. München (Germany); Markus Betz, Technische Univ. Dortmund (Germany)
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We report on two sets of experiments whereby femtosecond near-infrared pulses are utilized to demonstrate optoelectronic functionalities of nanodevices. First, coherent control techniques are used to generate ballistic photocurrents in nanowires. In particular, illuminating a GaAs nanowire with a phase stable superposition of 1550 nm femtosecond pulses and their second harmonic, ~ตA ballistic electrical currents are generated without an external bias. The second part is related to the excitation of surface plasmon polaritons (SPPs) in plain and unstructured gold films. In contrast to established SPP launchers based on permanent gratings, we utilize LiNbO_3 surface acoustic waves underneath a metal thin film to create dynamic gratings with variable period and amplitude as well as nanosecond switching times.

Fs-induced apodised Bragg waveguides in fused silica

Paper 7925-48 of Conference 7925
Date: Monday, 24 January 2011
Time: 4:10 PM – 4:30 PM

Author(s): Christian Voigtländer, Friedrich-Schiller-Univ. Jena (Germany); Peter Zeil, Royal Institute of Technology (Sweden); Jens Thomas, Andreas Tünnermann, Stefan Nolte, Friedrich-Schiller-Univ. Jena (Germany)
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Femtosecond laser pulsed inscription techniques allow non-photosensitive and active glasses to serve as platforms for integrated devices. Bragg waveguides represent essential building blocks providing both narrow and broad-band integrated mirrors. However, femtosecond pulse written broad-band Bragg waveguides have yet suffered from poor apodisation resulting in unwanted side-lobes. Here we present apodised Bragg waveguides inscribed in fused silica using a high repetition rate laser system with a pulse picker. By varying its modulation, the mean refractive index over the grating length could be kept constant, while the grating strength is varied. Thus, Bragg waveguides with Gaussian modulation profiles could be demonstrated.

1100W Yb:YAG fs INNOSLAB amplifier

Paper 7912-28 of Conference 7912
Date: Tuesday, 25 January 2011
Time: 10:50 AM – 11:20 AM

Author(s): Peter Russbueldt, Fraunhofer-Institut für Lasertechnik (Germany); Torsten G. Mans, RWTH Aachen (Germany); Hans-Dieter Hoffmann, Reinhart Poprawe, Fraunhofer-Institut für Lasertechnik (Germany)
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To transfer femtosecond technology to industrial applications, laser sources of high average power are essential. We demonstrate a compact diode-pumped Yb:KGW femtosecond oscillator - Yb:YAG Innoslab amplifier MOPA with nearly transform and diffraction limited 636 fs pulses at 620 W average output power and 20 MHz repetition rate. By cascading two amplifiers an average output power of 1.1 kW and peak power of 80 MW is achieved in a single, linearly polarized beam. The MOPA is operated at room temperature and no CPA technique is used. The specific properties of Innoslab MOPAs are compared with fibers and thin-disks.

Laser-based synthesis in liquid environment of silicon nanoparticles and their related structural and optical properties

Paper 7922-24 of Conference 7922
Date: Tuesday, 25 January 2011
Time: 6:00 PM

Author(s): Romuald Intartaglia, K. Bagga, Fernando Brandi, G. Das, A. Genovese, E. Di Fabrizio, Alberto Diaspro, Istituto Italiano di Tecnologia (Italy)
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Silicon nanoparticles (Si-NPs) are of great interest due to their unique physical properties which make them suitable for a wide range of applications specially in the production of nanostructured materials with tailor made properties to be used in the field of medicine, energy technology and in particular in bio-medicine as efficient photosensitizers of oxygen molecule [1]. Recently, it was demonstrated that Si-NPs can generate singlet oxygen state upon UV-irradiation [2]. So far, a variety chemical approach such as electrochemical etching, wet chemistry route was developed to produce Si-NPs [3,4]. In the last decade, the production of nanomaterials by laser based-synthesis, started to represent an alternative to the chemical ones which could be inconvenient for certain applications owing to the contamination of the resulted nanomaterials [5]. The use of toxic compound during the chemical synthesis procedure complicates their applications in, in vivo biosensing and imaging. Laser ablation of a solid target in liquid environment allows the production of colloid nanocrystals with unique surface chemistry (free from any contaminant) since the synthesis is carried out in a contamination-free environment. Many irradiations parameters have to be taking in account for controlling the size and shape of nanoparticles. Some of these parameters include laser wavelength, pulse energy, pulse duration, repetition rate, and liquid environments [6-9]. In particular, the laser pulse duration is found to affect directly the ablation, nucleation, growth, and aggregation mechanisms. Long laser pulses (nanosecond) release energy on a time-scale comparable with the thermal relaxation processes of the target, while femtosecond laser pulses release energy to electrons in the target on a time-scale much faster than electron-phonon thermalization processes. Thus local heating on the target is reduced in the case of femtosecond pulse. Moreover temporal overlap between laser pulses and the ablated material induces thermodynamic instability of the plasma during his expansion. Consequently, some differences are observed in the generated nanoparticles with pulses of different duration . Only few works on silicon nanoparticles generation in liquid environment has been reported [10,11]. Nanosecond laser ablation of silicon show generation of nanoparticles which stabilize into clusters due to agglomeration effect. ie Silicon nanoparticles are held together by an irregular network. Here, isolated silicon nanoparticles were prepared by femtosecond laser ablation of a silicon target in deionized water. The mean size is found to vary from 60 nm to 2.5 nm in the absence of any reducing chemical reagents, decreasing the laser fluence of one order of magnitude (Fig.1). High resolution transmission electronic microscopy together with Raman spectroscopy confirms the crystalline structure of the generated silicon nanoparticles. The energy confinement of carriers which is evaluated from optical experiment varies from 90 meV to 550 meV when the mean nanoparticles size decrease from 60 nm to 2.5 nm. In particular, the evaluated nanoparticles size from optical analysis and LCAO theoretical model are found in agreement with TEM and Raman measurements for the silicon nanoparticles with a size less than 6 nm. Moreover, agglomeration effect is observed for smallest nanoparticles produced at lower fluence.

Spatiotemporal beam control of an OPCPA laser system

Paper 7916-38 of Conference 7916
Date: Tuesday, 25 January 2011
Time: 6:00 PM

Author(s): Xiaoming Zeng, Chinese Academy of Engineering Physics (China)
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An arbitrary spatiotemporal beam shaping technique is proposed. An OPCPA laser system owning this ability is being constructed. The frond end seed of this OPCPA laser system is a millijoule-level 1053nm wavelength femtosecond clean pulse. This large energy clean seed pulse, which insures the high signal-noise-ratio of the whole laser system, is obtained through a femtosecond optical parametric amplification system based on Supercontinuum White Light injection. As our OPCPA experiments show, temporal shape (spectrum) of the signal pulse can be valid controlled by the pump pulse shaping which is modulated by an Arbitrary Wave-shape Generator. Shaping the pump pulse nearfield distribution by a liquid crystal can also realize a well nearfield shaping of the amplified signal pulse.

Three-dimensional structuring inside transparent materials by a phase modulated fs laser beam with a LCOS-SLM

Paper 7920-38 of Conference 7920
Date: Wednesday, 26 January 2011
Time: 3:30 PM – 4:00 PM

Author(s): Masaaki Sakakura, Kiyotaka Miura, Kyoto Univ. (Japan); Tsutomu Sawano, New Glass Forum (Japan); Yasuhiko Shimotsuma, Kyoto Univ. (Japan); Kazuyuki Hirao, New Glass Forum (Japan)
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A femtosecond laser processing system with a spatial light modulator (SLM) and its application are presented. Three-dimensional refractive index structures can be fabricated inside glasses by foscuing femtosecond laser pulses. To induce large refractive index increase without crack formation, irradiation time is needed. Therefore, fabrication efficiency is a critical problem. Our laser processing system with an SLM can improve the fabrication efficiency, because multiple light spots can be generated by modulating the spatial phase distribution of laser beam with an SLM. We will talk about the principle of the laser machining system as well as the applications for parallel writing of 3D optical waveguides, diffractive gratings, and optical data strage.

Laser processing inside transparent materials: dependence on pulse length and wavelength

Paper 7926-5 of Conference 7926
Date: Thursday, 27 January 2011
Time: 10:50 AM – 11:10 AM

Author(s): Udo Loeschner, Joerg Schille, Robby Ebert, Horst Exner, Hochschule Mittweida (Germany)
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This paper discusses the processing of transparent materials using various laser sources emitting short pulses (nanoseconds) and ultrashort pulses (femtoseconds) at different wavelengths. In our study we investigated in detail the dependencies of controlled micro defect generation inside bulk glass (BK glass, fused silica) and polymer (polymethylmethacrylate, polycarbonate, cyclo-olefin-copolymers) on important process parameters like wavelength, pulse width, and irradiation regime. By applying an irradiation regime with optimal process parameters these local confined material destructions can be arranged in cut surfaces in order to cut 3d parts, consisting of bulk transparent material.

Course: Ultrafast Fiber Lasers

Date: Sunday, 23 January 2011
Time: 8:30 AM – 12:30 PM

Instructor(s): Martin E. Fermann, IMRA America, Inc. (United States)
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Starting from an introduction to fiber lasers, basic properties of fiber amplifiers are reviewed and current state of the art fiber amplifier technology is summarized. The course then describes preferred construction methods for ultrafast fiber lasers and frequency combs and discusses their applications in a variety of optical systems. The course covers mode locked fiber oscillators, phase stabilization techniques, supercontinuum sources, ultrafast fiber amplifiers, frequency converters as well as pulse compressors. Numerous design examples are given, illustrating the recurring physical phenomena governing these systems. The attendee learns about preferred methods for pico- and femtosecond pulse generation in compact fiber systems and basic modeling techniques for pulse evolution, stability, jitter and noise. The course concludes with overviews of applications in materials processing, frequency metrology, spectroscopy and optical sampling.

Course: Terahertz Wave Technology and Applications

Date: Wednesday, 26 January 2011
Time: 8:30 AM – 12:30 PM

Instructor(s): Xi-Cheng Zhang, Rensselaer Polytechnic Institute (United States)
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A pulsed terahertz (THz) wave with a frequency range from 0.1 THz to 10 THz is called a "T-ray." T-rays occupy a large portion of the electromagnetic spectrum between the infrared and microwave bands. However, compared to the relatively well-developed science and technology in the microwave, optical, and x-ray frequencies for defense and commercial applications, basic research, new initiatives and advanced technology developments in the THz band are very limited and remain unexplored. However, just as one can use visible light to create a photograph, radio waves to transmit music and speech, microwave radiation (MRI) or X-rays to reveal broken bones, T-ray can be used to create images or communicate information. This course will provide the fundamentals of free-space THz optoelectronics. We will cover the basic concepts of generation, detection, propagation, and applications of the T-rays, and how the up-to-date research results apply to industry. The free-space T-ray optoelectronic detection system, which uses photoconductive antennas or electro-optic crystals, provides diffraction-limited spatial resolution, femtosecond temporal resolution, DC-THz spectral bandwidth and mV/cm field sensitivity. Examples of homeland security and defense related projects will be highlighted.

Ultrafast carrier and phonon dynamics in graphene: relaxation, recombination, and transport

Paper 7937-61 of Conference 7937
Date: Wednesday, 26 January 2011
Time: 1:25 PM – 1:50 PM

Author(s): Farhan Rana, Haining Wang, Jared H. Strait, Cornell Univ. (United States)
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In this talk we discuss our experimental and theoretical results on the ultrafast dynamics of carriers and phonons in graphene. Ultrafast optical and terahertz spectroscopy results show that photoexcited carriers in graphene exhibit multiple time scales while undergoing relaxation and recombination dynamics. Hot carriers lose most of their energy to optical phonons within few hundred femtoseconds resulting in a hot phonon population which then becomes the main bottleneck for carrier cooling. Hot optical phonons decay into acoustic phonons via anharmonic processes within a few picoseconds. We will discuss the relevance of our experimental and theoretical results to graphene based optoelectronics.

Microscopic theory of ultrafast processes in carbon nanomaterials

Paper 7937-62 of Conference 7937
Date: Wednesday, 26 January 2011
Time: 1:50 PM – 2:15 PM

Author(s): Ermin Malic, Torben Winzer, Andreas Knorr, Technische Univ. Berlin (Germany)
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We have performed microscopic investigations of the phonon- and Coulomb-induced relaxation dynamics of photo-excited carriers in graphene and single-walled carbon nanotubes. Based on microscopic calculation within the density matrix formalism we show that the electron-electron scattering thermalizes the electronic system within first hundred femtoseconds followed by a fast energy dissipation arising from the electron-phonon coupling. Furthermore, we show that due to its zero-bandgap Auger-type processes play an unusually significant role for understanding the carrier dynamics in graphene. In particular, we observe a considerable carrier multiplication due to the efficient impact ionization.

Femto second single optical fiber tweezers enabled two-photon fluorescence excitation of trapped microscopic objects

Paper 7925-4 of Conference 7925
Date: Sunday, 23 January 2011
Time: 10:00 AM – 10:20 AM

Author(s): Yogeshwar N. Mishra, Cochin Univ. of Science & Technology (India); Ninad D. Ingle, Samarendra K. Mohanty, The Univ. of Texas at Arlington (United States)
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Analysis of trapped microscopic objects using fluorescence and Raman spectroscopy is gaining considerable interest. We report on the development of single fiber femto second optical tweezers and its use in two-photon fluorescence excitation (TPE) of trapped fluorescent polystyrene beads. We will present theoretical simulation of femtosecond fiber optical microbeam profiles emerging from the axicon tip and the experimentally observed TPE patterns. The combined use of TPE and optical trapping using single fiber optical tweezers will enable in-depth analysis of non-adherent samples.

In-vivo coherent Raman scattering imaging with a periodically poled crystal OPO

Paper 7903-90 of Conference 7903
Date: Sunday, 23 January 2011
Time: 5:30 PM

Author(s): Delong Zhang, Mikhail N. Slipchenko, Yunzhou Shi, Ji-Xin Cheng, Purdue Univ. (United States)
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We demonstrate a new microscope for highly sensitive coherent anti-Stokes Raman scattering (CARS) and stimulated Raman scattering (SRS) imaging. By using femtosecond pulse excitation and a high-power Stokes beam provided by a periodically poled crystal OPO tunable from 1.0 to 1.6 micron, our setup provides CARS and SRS signals that are more than 10 times larger than current systems using picosecond pulses. The high signal levels enable high-quality CARS and SRS imaging of live animals with a fast acquisition rate.

Spectrally resolved CARS microscopy of condensed carbohydrate systems

Paper 7903-112 of Conference 7903
Date: Sunday, 23 January 2011
Time: 5:30 PM

Author(s): Aaron D. Slepkov, Andrew Ridsdale, Adrian F. Pegoraro, Douglas J. Moffatt, Albert Stolow, National Research Council Canada (Canada)
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We utilize a single-source femtosecond-laser-based multimodal nonlinear optical CARS microscope to image condensed carbohydrate systems such as starch, cellulose, and glycogen. The bright CARS signals from such biologically-relevant materials opens new vistas for CARS microscopy beyond traditional lipid imaging. Our added ability of rapid spectral scanning allows for spatially-resolved spectroscopic imaging of these systems, and elucidates stark contrasts in their respective CARS spectra.

Ultrafast microsphere near-field nanostructuring

Paper 7925-40 of Conference 7925
Date: Tuesday, 25 January 2011
Time: 3:30 PM – 3:50 PM

Author(s): Karl-Heinz Leitz, Ulf Quentin, Lehrstuhl für Photonische Technologien (Germany) and Erlangen Graduate School of Advanced Optical Technologie (Germany); Benjamin Hornung, Consultant (Germany); Andreas Otto, Ilya Alexeev, Michael Schmidt, Lehrstuhl für Photonische Technologien (Germany) and Erlangen Graduate School of Advanced Optical Technologie (Germany)
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The utilisation of non-linear multi-photon and near-field effects allows a sub-diffraction limited laser based nanostructuring. In this contribution a basic study of the influence of processing parameters on the microsphere near-field nanostructuring with ultrashort pico- and femtosecond laser pulses will be presented. The experimental and numerical results with dielectric and metal nanoparticles on dielectric, semiconductor and metal substrates show the influence of particle size and material, substrate material, pulse duration, number of contributing laser pulses and polarisation on the structuring process.

Ultrafast microsphere near-field nanostructuring

Paper 7920-40 of Conference 7920
Date: Tuesday, 25 January 2011
Time: 3:30 PM – 3:50 PM

Author(s): Karl-Heinz Leitz, Ulf Quentin, Lehrstuhl für Photonische Technologien (Germany) and Erlangen Graduate School of Advanced Optical Technologie (Germany); Benjamin Hornung, Consultant (Germany); Andreas Otto, Ilya Alexeev, Michael Schmidt, Lehrstuhl für Photonische Technologien (Germany) and Erlangen Graduate School of Advanced Optical Technologie (Germany)
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The utilisation of non-linear multi-photon and near-field effects allows a sub-diffraction limited laser based nanostructuring. In this contribution a basic study of the influence of processing parameters on the microsphere near-field nanostructuring with ultrashort pico- and femtosecond laser pulses will be presented. The experimental and numerical results with dielectric and metal nanoparticles on dielectric, semiconductor and metal substrates show the influence of particle size and material, substrate material, pulse duration, number of contributing laser pulses and polarisation on the structuring process.

Multimodal nonlinear optical polarizing microscopy of long-range orientational order in liquid crystals

Paper 7955-10 of Conference 7955
Date: Tuesday, 25 January 2011
Time: 5:00 PM – 5:30 PM

Author(s): Ivan I. Smalyukh, Rahul P. Trivedi, Taewoo Lee, Univ. of Colorado at Boulder (United States)
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We demonstrate orientation-sensitive multimodal nonlinear optical polarizing microscopy capable of probing orientational, polar, and biaxial features of mesomorphic ordering in soft matter systems such as liquid crystals. This technique achieves simultaneous imaging in broadband coherent anti-Stokes Raman scattering, multi-photon excitation fluorescence, and multi-harmonic generation polarizing microscopy modes and is based on the use of a single femtosecond laser and a photonic crystal fiber as sources of the probing light. We demonstrate the viability of this technique for mapping of 3D patterns of molecular orientations and show that images obtained in different microscopy modes are consistent with each other.

Ultrashort pulse induced nonlinear photo-polymerization and phase separation in liquid crystal and monomer mixtures

Paper 7927-38 of Conference 7927
Date: Tuesday, 25 January 2011
Time: 6:00 PM

Author(s): Kuei-Chu Hsu, Yao-Teng Tseng, National Central Univ. (Taiwan)
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Mechanism of nonlinear photo-polymerization and phase separation in liquid crystal and monomer mixture is investigated. Micrograting-like polymer route is formed when frequency-doubled Ti:sapphire femtosecond pulse with wavelength of 370 nm and average power of 100-mW exposes on pure monomer thin film at high scanning speed. Large-size liquid crystal droplet grating and complicated donut pattern in thin mixture film containing nematic liquid crystal and monomer are further observed due to ultrashort-pulse-induced nonlinear polymerization and phase separation.

Two-photon time-resolved confocal microscopy using a digital micromirror device

Paper 7932-16 of Conference 7932
Date: Wednesday, 26 January 2011
Time: 4:20 PM – 4:40 PM

Author(s): Markus Schellenberg, Michael Kloster, Eltimir Peev, James Napier, Walter Neu, Fachhochschule Oldenburg/Ostfriesland/Wilhelmshaven (Germany)
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By two-photon time-resolved confocal 4D-microscopy it is possible to image fluorescent objects at a high spatial and temporal resolution. The usage of femtosecond-laser light creates a two photon effect and therefore reduces bleaching of the fluorophore. With this technique 4D visualization of dynamic processes in living cells is possible.

Technology needs for corneal transplant surgery (Keynote Presentation)

Paper 7885-12 of Conference 7885
Date: Saturday, 22 January 2011
Time: 11:30 AM – 12:15 PM

Author(s): Sonia H. Yoo, Bascom Palmer Eye Institute (United States)
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Corneal transplant surgery has undergone numerous modifications over the years with improvements in technique, instrumentation and eye banking. The main goals of corneal transplantation are achieving excellent optical clarity with long-term graft survival. Penetrating, anterior and posterior lamellar surgery along with femtosecond laser technology have partially met these goals, but outcomes are often unpredictable and surgeon dependent. Technology to predictably separate stroma from Descemet's membrane, techniques to minimize endothelial cell loss, improvements in imaging technology and emerging techniques like laser welding that might replace suturing, eventually making corneal transplantation a refractively predictable procedure are on the wish list of the cornea surgeon.

Novel Uses of Femtosecond Laser Pulses in Biophotonics

Date: Saturday, 22 January 2011
Time: 8:55 PM – 9:05 PM

Author(s):
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Eric Mazur, Harvard Univ. (USA)

Selective analyte adsorption on mixed-metal SERS substrates

Paper 7911-7 of Conference 7911
Date: Sunday, 23 January 2011
Time: 9:20 AM – 9:40 AM

Author(s): Philip A. Munoz, Paul Peng, Roberto Olivares-Amaya, Alán Aspuru-Guzik, Harvard Univ. (United States)
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We present the effect of mixed metals on the preferential binding of analyte molecules to femtosecond-laser structured SERS substrates. By coating a native gold- or silver-based SERS substrate with an additional thin layer of nickel, platinum, or palladium atoms, we show that preferential binding to molecules with primary amine groups may be achieved, resulting in an improvement to the Raman enhancement over a native SERS substrate. Our results are supported by time-dependent density functional theoretical calculations. We examine the impact of type and thickness of transition metal, and the applicability of these substrates to sensitive detection of biological molecules.

New developments in clinical multiphoton tomography (Keynote Presentation)

Paper 7903-3 of Conference 7903
Date: Sunday, 23 January 2011
Time: 9:35 AM – 10:05 AM

Author(s): Karsten Koenig, Univ. des Saarlandes (Germany)
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The multiphoton tomographs DermaInspect™ and MPTflex™ are novel clinical skin imaging devices using a near-infrared femtosecond laser source. Non-linear excitation allows to detect natural endogenous fluorophores inside human skin such as NAD(P)H, flavins, elastin, collagen, melanin, keratin, and porphyrins down to a tissue depth of 200 ตm without applying any contrast agents. Individual intratissue cells, intracellular mitochondria, melanosomes, and the morphology of the nuclei as well as extracellular matrix elements can be imaged. In vivo 5D imaging can be realized based on spectral fluorescence lifetime imaging. So far, more than 1,000 patients and volunteers in Europe, Asia, and Australia have been investigated with these novel molecular imaging tools. Current developments include the production of multimodal hybrid systems such as the combination with ultrasound, optical coherence tomography, diffuse reflectance, and CARS.

Visualization of the first hyperpolarizability tensor elements with second-harmonic generation microscopy in biological spherocrystals

Paper 7903-11 of Conference 7903
Date: Sunday, 23 January 2011
Time: 1:25 PM – 1:40 PM

Author(s): Virginijus Barzda, Richard Cisek, Adam E. Tuer, Univ. of Toronto Mississauga (Canada)
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Direct visualization of the first hyperpolarizability is achieved in radially arranged crystals using second harmonic generation (SHG) microscopy. Two structurally similar biological spherocrystals were investigated; starch, energy storage organelles in plant cells, and otoconia, sensors of linear acceleration in mammals. The radial organization of these structures allows direct visualization of hyperpolarizability tensor elements using polarization SHG microscopy. Differential microscopy using two identical time-shifted femtosecond Yb:KGW beams was used to determine tensor elements from single scans. SHG microscopy is sensitive to small variations in crystalline structure and therefore is extremely beneficial for starch quality control and medical diagnosis of otoconia diseases.

Toward determinism in surface damaging of dielectrics using few-cycle laser pulses

Paper 7937-19 of Conference 7937
Date: Monday, 24 January 2011
Time: 8:00 AM – 8:25 AM

Author(s): Nicolas Sanner, Olivier Utéza, Benoît Chimier, Marc Sentis, Lasers, Plasmas et Procédés Photoniques (France); Philippe Lassonde, François Légaré, Jean-Claude Kieffer, Institut National de la Recherche Scientifique (Canada)
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We present a quantitative measurement of the degree of determinism in femtosecond laser-induced damaging at the surface of a dielectric material. We demonstrate that laser damage occurrence tends to be dramatically deterministic for few-cycle pulses, which is attributed to the increasing importance of tunnelling ionization as the major channel for the generation of free-carriers in the conduction band. Parallel investigation of ablation thresholds reveals a strong decrease for damage and ablation thresholds, that merge at ultrashort pulse durations. A numerical model based on Keldysh theory, using appropriate thresholds criteria, reproduce accurately the evolution of thresholds on the whole sub-picosecond range.

Biosensing of single cells at GHz frequencies by laser-ultrasonics

Paper 7899-32 of Conference 7899
Date: Monday, 24 January 2011
Time: 9:00 AM – 9:15 AM

Author(s): Bertrand Audoin, Mathieu Ducousso, Thomas Dehoux, Univ. Bordeaux 1 (France); Céline Chollet, Omar Zouani, Christel Chanseau, Marie-Christine Durrieu, Univ. Victor Segalen Bordeaux 2 (France)
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We use femtosecond laser pulses absorbed in a TiAl4V alloy, namely the picosecond ultrasonics technique, for the remote optical generation and detection of acoustic frequencies ~30 GHz in single MC3T3 cells. The alloy is functionalized with a RGD peptide layer and a BMP2 protein is used to stimulate cell adhesion. The result of a semi-analytical calculation is fitted to the experimental data to determine simultaneously the sound velocity at ~30 GHz and the nanometer thickness of single cells. Statistical variations in the sound velocity reveal nanoscale modifications of the cell cytosqueletal structure upon BMP2-induced reorganization.

Carrier dynamics investigation in quantum cascade lasers using ultrafast pulses

Paper 7937-25 of Conference 7937
Date: Monday, 24 January 2011
Time: 11:00 AM – 11:15 AM

Author(s): Sheng Liu, Elaine Lalanne, Robinson A. Kuis, Anthony M. Johnson, Univ. of Maryland, Baltimore County (United States)
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We employ femtosecond Mid-IR time-resolved pump-probe technique to investigate the nature of carrier transport in QCLs. Gain recovery and amplification of probe pulses are observed near threshold and at low bias, respectively. This is due to the interaction between strong pump pulses and electrons, which reveals the population difference between upper and lower lasing states. When biased near threshold, following a fast (shorter than 200fs) gain recovery, oscillation of the probe signal is observed within the first picosecond. This oscillation can not be seen when pump power is attenuated. Slower gain recovery with lifetime of 3-4ps is later seen.

Plasmonic and two-photon luminescence of star-like gold nanoparticles used in cervical cancer detection

Paper 7911-31 of Conference 7911
Date: Monday, 24 January 2011
Time: 11:30 AM – 11:50 AM

Author(s): Saul Ruiz, Tzarara Lopez-Luke, Ctr. de Investigaciones en Óptica, A.C. (Mexico); Ana Lilia Gonzalez, Univ. de Guanajuato (Mexico); Roxana Cerbantez, Ctr. de Investigaciones en Óptica, A.C. (Mexico); Pedro Salas, Univ. Nacional Autónoma de México (Mexico); Elder De La Rosa, Ctr. de Investigaciones en Óptica, A.C. (Mexico)
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Nanoparticles were prepared at room temperature with citric acid with a size ranging from 160 nm to 180 nm, controlled with short time reactions and using seeds nanoparticles. It is presented the method to functionalize the gold nanoparticles to label Ki-67 cervical protein of exfoliated cervical cancer cells. Ki-67 is a nuclear antigen associated to cells proliferation. Different methods to study the capacity of diffusion of nanoparticles were evaluated. Experimental results show a high fluorescence of gold nanoparticles imaging the cervical cells and the destruction by photothermal effect. Results suggest that fluorescence was produced by two-photon absorption after pumping at 720 nm from a femtosecond laser.

High-brightness distributed-Bragg-reflector tapered diode lasers: pushing your application to the next level

Paper 7918-26 of Conference 7918
Date: Monday, 24 January 2011
Time: 1:40 PM – 2:00 PM

Author(s): Christian Fiebig, Ferdinand-Braun-Institut (Germany); Selina Pekarek, ETH Zurich (Switzerland); Mirko Uebernickel, Ferdinand-Braun-Institut (Germany); Thomas Südmeyer, Ursula Keller, ETH Zurich (Switzerland); Katrin Paschke, Götz Erbert, Ferdinand-Braun-Institut (Germany)
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The development of monolithic Distributed-Bragg-Reflector diode lasers having a brightness close to 1 GWcm-2sr-1 enabled new applications and the miniaturization of established setups. We generated visible light up to 1.8 W in a single-pass SHG bench top experiment and demonstrated 1 W with a compact micro-module. Furthermore, the diode laser was used as pump laser for a femtosecond gigahertz SESAM-modelocked Yb:KGW with a record high peak power of 3.9 kW. At the repetition rate of 1 GHz 281-fs pulses with an average output power of 1.1 W were generated. This Yb:KGW laser has a high potential for stable frequency comb generation.

Integrated multiplex CARS and two-photon fluorescence microscopy for imaging biological systems

Paper 7903-37 of Conference 7903
Date: Monday, 24 January 2011
Time: 1:49 PM – 2:01 PM

Author(s): Dong Li, Wei Zheng, Jianan Y. Qu, Hong Kong Univ. of Science and Technology (Hong Kong, China)
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A multimodal nonlinear optical microscopy that combines the multiplex coherent anti-stokes Raman scattering (M-CARS) signals with the two-photon excitation fluorescence (TPEF) has been developed. The excitation sources are a femtosecond laser and the broadband supercontinuum from photonic crystal fiber. The large non-resonant signals in the femotosecond laser excited CARS images was effectively suppressed by using a simple subtraction method. The nonlinear optical signals of M-CARS, TPEF, and second harmonic generation (SHG) are simultaneously excited and collected by a time- and wavelength-resolved detection capability. We demonstrate the multimodal imaging capability using the C.elegnas and 3T3-L1 cells as the living biological samples.

Industrial production with ultra fast laser workstations

Paper 7925-18 of Conference 7925
Date: Tuesday, 25 January 2011
Time: 9:40 AM – 10:00 AM

Author(s): Eric Audouard, Univ. Jean Monnet Saint-Etienne (France); Hervé Soder, Impulsion SAS (France)
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In this work, we will underline some practical applications and the link between a better knowledge of physical mechanisms and the development of industrial processes. Of course, we have to pay attention to typical parameters of industrial development, such as the processing time. For instance, the physical time can be easily calculated, using the total length of the machining, speed and laser parameters. This calculated physical process time can be compared to the effective time needed to machine the sample. Femtosecond technology has now proven its capacity to lead innovative production, even if it's still in some well defined fields, but its contribution is non negligible in a context of economical crisis.

Industrial production with ultra fast laser workstations

Paper 7920-18 of Conference 7920
Date: Tuesday, 25 January 2011
Time: 9:40 AM – 10:00 AM

Author(s): Eric Audouard, Univ. Jean Monnet Saint-Etienne (France); Hervé Soder, Impulsion SAS (France)
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In this work, we will underline some practical applications and the link between a better knowledge of physical mechanisms and the development of industrial processes. Of course, we have to pay attention to typical parameters of industrial development, such as the processing time. For instance, the physical time can be easily calculated, using the total length of the machining, speed and laser parameters. This calculated physical process time can be compared to the effective time needed to machine the sample. Femtosecond technology has now proven its capacity to lead innovative production, even if it's still in some well defined fields, but its contribution is non negligible in a context of economical crisis.

Thresholds for laser-induced DNA damage in nonlinear microscopy

Paper 7903-60 of Conference 7903
Date: Tuesday, 25 January 2011
Time: 9:40 AM – 9:55 AM

Author(s): Oleg Nadiarnykh, Utrecht Univ. (Netherlands); Giju Thomas, Erasmus MC (Netherlands); Johan van Voskuilen, Utrecht Univ. (Netherlands); Henricus J. C. M. Sterenborg, Erasmus MC (Netherlands); Hans C. Gerritsen, Utrecht Univ. (Netherlands)
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Focused femtosecond laser pulses have been shown to cause DNA damage due to three-photon absorption. We quantified DNA damage introduced in ovarian hamster cells in vitro using fluorescent antibodies against cyclobutane-pyrimidin-dimers, where three-photon absorption was confirmed by cubic dependence of fluorescence on excitation power. We further investigated the extent of CPD damage with respect to excitation wavelength between 690 and 820nm, pulsewidth at focal plane varied with custom-built grating pair, and pixel dwell time as compared to more pronounced damage from solar simulator UV source. Damage thresholds are identified for several wavelengths, and relatively safe imaging regimes are suggested.

Quasi-ballistic thermal transport from nanoscale interfaces observed using ultrafast coherent soft x-ray beams

Paper 7937-41 of Conference 7937
Date: Tuesday, 25 January 2011
Time: 11:35 AM – 12:00 PM

Author(s): Mark E. Siemens, Univ. of Denver (United States); Qing Li, Ronggui Yang, Univ. of Colorado at Boulder (United States); Keith A. Nelson, Massachusetts Institute of Technology (United States); Erik H. Anderson, Lawrence Berkeley National Lab. (United States); Margaret M. Murnane, Henry C. Kapteyn, Univ. of Colorado at Boulder (United States)
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Heat dissipation from a nanoscale hot-spot is expected to be non-diffusive for hot-spots smaller than the phonon mean free path of the substrate. Our technique of observing diffraction of coherent soft x-ray pulses allows for very high resolution (~pm) of surface distortion, as well as femtosecond time resolution of dynamics. We successfully model our experimental results with a diffusive transport model, modified to include an additional boundary resistance. These results confirm the importance of considering ballistic transport away from a nanoscale heat source, and identify a means of correctly accounting for this ballistic transport.

Trends in nanoplasmonics: ultrasmall, ultrafast, ultrastrong

Paper 7937-42 of Conference 7937
Date: Tuesday, 25 January 2011
Time: 1:30 PM – 1:55 PM

Author(s): Mark I. Stockman, Georgia State Univ. (United States)
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Nanoplasmonics deals with collective electron dynamics on the surface of metal nanostructures, which arises as a result of excitations called surface plasmons. The surface plasmons localize and concentrate optical energy in nanoscopic regions creating highly enhanced local optical fields. They undergo ultrafast dynamics with timescales as short as a few hundred attoseconds. From the latest developments and original work in nanoplasmonics, we will consider SPASER (quantum nanoscale optical generator and ultrafast amplifier), ultrafast coherent control on the nanoscale, generation of EUV radiation by plasmonic enhancement, adiabatic nano-concentration of optical energy, and SPIDER (surface-plasmon-induced drag-effect rectification) that leads to generation of nanoscale THz fields by femtosecond polaritonic pulses in metal nanowires.

Terahertz generation with tilted-front laser pulses: dynamical theory

Paper 7917-18 of Conference 7917
Date: Tuesday, 25 January 2011
Time: 2:40 PM – 3:00 PM

Author(s): Michael I. Bakunov, Univ. of Nizhny Novgorod (Russian Federation); Sergey B. Bodrov, Institute of Applied Physics (Russian Federation); Eugene Mashkovich, Univ. of Nizhny Novgorod (Russian Federation)
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A theory of terahertz emission from a femtosecond laser pulse with tilted intensity front propagating through a prism-shaped electro-optic crystal is developed. The theory accounts for transient effects at the entrance boundary of the crystal and allows one to explore the dynamics of terahertz generation in the crystal. Typical experimental situations - LiNbO3 excited with Ti:sapphire laser at room and cryogenic temperatures - are considered, and new schemes - GaAs excited at 1.8 and 3.5 um - are proposed and analyzed. The parameters of the laser pulse (transverse size, tilt angle, and pulse duration) and crystal size maximizing the terahertz yield are calculated.

Tailored hybrid materials for sub-100 nm two-photon lithography and micro optical applications

Paper 7927-13 of Conference 7927
Date: Tuesday, 25 January 2011
Time: 3:10 PM – 3:30 PM

Author(s): Sönke Steenhusen, Ferdinand Landgraf, Ruth Houbertz, Fraunhofer-Institut für Silicatforschung (Germany)
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Recent work on the rapid prototyping of hybrid polymers (ORMOCERฎs) using visible and infrared femtosecond laser pulses is presented. To pursue the goal of sub-100 nm voxel sizes in two-photon-polymerization (2PP), specially tailored ORMOCERฎs are investigated, and the impact of illumination parameters and radical inhibitors is discussed. Feature sizes below 100 nm can easily be achieved. Furthermore, the cross-linking behavior of 2PP-fabricated structures is quantified using ต-Raman spectroscopy, and is compared to one-photon exposure. Besides, these fundamental studies on the photochemical processes behind 2PP, different three-dimensional structures are shown, which can for example be used as micro optical elements.

Parabolic pulse generation in the nonlinear nonuniform fibre cascade

Paper 7917-65 of Conference 7917
Date: Tuesday, 25 January 2011
Time: 6:00 PM

Author(s): Igor Zolotovsky, Marina Yavtushenko, Ulyanovsk State Univ. (Russian Federation); Alexej A. Sysoliatin, A. M. Prokhorov General Physics Institute (Russian Federation); Dmitry I. Sementsov, Igor Yavtushenko, Ulyanovsk State Univ. (Russian Federation); Oleg Okhotnikov, Tampere Univ. of Technology (Finland)
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Dynamics of optical pulses in the cascade of two longitudinally non-uniform nonlinear fibres is investigated theoretically and experimentally. The first part of the cascade is necessary for pulse chirp management. In the second part of the cascade the pulse average form changes. Profiles of fibre non-uniformity are picked up so that the impulse is transformed to the parabolic form. Compression and nonreciprocal dynamics of the frequency-modulated pulses in such cascades is investigated as well. The picosecond initial pulse is compressed to 100 femtosecond in the 20-metres-length cascade with a normal dispersion.

Course: Nanoplasmonics

Date: Wednesday, 26 January 2011
Time: 8:30 AM – 5:30 PM

Instructor(s): Mark I. Stockman, Georgia State Univ. (United States)
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Nanooptics deals with optical phenomena and spectroscopy on the nanoscale, i.e., in the regions of space whose size is much smaller than the light wavelength. While electromagnetic waves cannot be localized in the regions with sizes significantly less than half wavelength, nanooptics is based on electric fields oscillating at optical frequency. From the positions of the interaction with matter and spectroscopy, such local optical fields mostly produce the same type of responses as electromagnetic waves. Elementary excitations that are carriers of energy and coherence in nanooptics are surface plasmons (SPs). These local fields cause a wealth of gigantically enhanced optical phenomena of which the surface enhanced Raman scattering (SERS) is the most studied and widely known. This one-day course will encompass the fundamental properties and applications of the surface plasmonics at the nanoscale. It will include coherent effects associated with phase memory of the SPs, in particular, coherent control of nanooptical phenomena. Nonlinear processes such as generation of harmonics and two-photon excitation by nanoscale fields will also be covered. Ultrafast (femtosecond and attosecond) phenomena are within the scope of this course. We will also include quantum phenomena associated with properties of surface plasmons as quantum quasiparticles such as quantum generation and fluctuations. Along with fundamental properties of SPs, we will consider many applications of nanoplasmonics, in particular, detection of ultrasmall amounts of chemical and biological compounds, scanning near-field optical microscopes or SNOMs, and nanolithography.

Novel aspects of pulse propagation in photonic crystal fibers

Paper 7946-33 of Conference 7946
Date: Wednesday, 26 January 2011
Time: 8:50 AM – 9:20 AM

Author(s): Sebastian P. Stark, Alexander V. Podlipensky, Philip S. Russell, Max-Planck Institute for the Science of Light (Germany)
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Unconventional wavelength-dependent group velocity dispersion, designed and realised in solid-core photonic crystal fibers (PCFs), can give rise to unusual pulse dynamics. Broad-band supercontinua can be generated in the visible spectral range, with high conversion efficiencies that can be further enhanced by frequent inter-soliton collisions. The high nonlinearity of small-core PCFs, along with a strongly uncompensated pulse chirp, can be used to trigger pulse breakup, leading to the generation of ultrashort THz pulse trains. Experimental and numerical results on the propagation of femtosecond pulses in axially-varying tapered PCF structures will also be discussed.

Photonic sensors for explosive detection

Paper 7945-87 of Conference 7945
Date: Wednesday, 26 January 2011
Time: 4:50 PM – 5:10 PM

Author(s): Ulrike Willer, Clausthal Univ. of Technology (Germany); Rozalia Orghici, Peter Lützow, Fraunhofer-Institut für Nachrichtentechnik Heinrich-Hertz-Institut (Germany); Wolfgang Schade, Technische Univ. Clausthal (Germany) and Fraunhofer-Institut für Nachrichtentechnik Heinrich-Hertz-Institut (Germany)
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Photonic sensors for the detection of explosives applying photoacoustics and evanescent field spectroscopy combined with silicon photonics and nano-dimensioned waveguides reveal entirely new possibilities for in-situ and real-time diagnostics. Specially engineered receptor films accumulate selectively TNT molecules which are detected very sensitively by evanescent field effects. A second photonic sensor is developed applying photoacoustic spectroscopy (QEPAS). Miniaturized laser technology in combination with silicon photonics and fiber optics enables engineering a smart handheld sensor, e.g. for the detection of TATP (tri-acetone tri-peroxide). Impulsive femtosecond laser excitation as new approach for selective multi-species excitation in combination with photoacoustic spectroscopy is also discussed.

ZnSe nanowires as harmonophores for multicontrast nonlinear microscopy

Paper 7946-48 of Conference 7946
Date: Wednesday, 26 January 2011
Time: 5:20 PM – 5:40 PM

Author(s): Richard Cisek, Univ. of Toronto Mississauga (Canada) and Institute for Optical Sciences (Canada); Alex Shik, Harry Ruda, Univ. of Toronto (Canada) and Centre for Advanced Nanotechnology (Canada); Virginijus Barzda, Univ. of Toronto Mississauga (Canada)
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ZnSe nanowires (NWs) can be used as biological labels for harmonic generation microscopy (harmonophores). The orientation dependency between linear polarization of the laser and the NW axis was investigated by recording the second and third harmonic generation as well as multiphoton induced fluorescence images with a nonlinear multicontrast microscope. Imaging individual NWs was achieved with a femtosecond Yb:KGW laser radiating at 1030 nm with 14 MHz pulse repetition rate. The angular dependencies revealed two major factors influencing the aforementioned nonlinearities: (i) the relative dielectric constant between NWs and their environment, and (ii) the surface roughness and bending of the NWs, revealing the latter effect can be dominant.

Nonlinear optical effects-induced spectral broadening in ZnO channel waveguides

Paper 7940-48 of Conference 7940
Date: Wednesday, 26 January 2011
Time: 6:00 PM

Author(s): Edgar Yoshio Morales Teraoka, Tomohiro Kita, Tohoku Univ. (Japan); Daniel H. Broaddus, Cornell Univ. (United States); Atsushi Tsukazaki, The Univ. of Tokyo (Japan) and PRESTO, Japan Science and Technology Agency (Japan); Masashi Kawasaki, Tohoku Univ. (Japan) and WPI Advanced Institute for Materials Research, Tohoku Univ. (Japan); Alexander L. Gaeta, Cornell Univ. (United States); Hirohito Yamada, Tohoku Univ. (Japan)
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We report the observation of enhanced nonlinear optical effects in ZnO channel waveguides. Our research is focused on obtaining waveguides with enhanced nonlinear properties. We demonstrate spectral broadening using femtosecond optical pulses at a wavelength of 840 nm. We obtained a maximum of six-fold broadening. Spectral features characteristic of SPM were appreciated. We calculated the nonlinear parameter gamma, obtaining values up to 13.9 W-1m-1. It represents more than 1300 times the gamma of a highly nonlinear fiber. Single-crystal ZnO showed to be a promising material for optical waveguides intended for nonlinear applications.

Soliton self-frequency shift in tellurite microstructured fiber

Paper 7934-38 of Conference 7934
Date: Wednesday, 26 January 2011
Time: 6:00 PM

Author(s): Xin Yan, Guanshi Qin, Meisong Liao, Takenobu Suzuki, Yasutake Ohishi, Toyota Technological Institute (Japan)
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In this paper, we report broad near-infrared soliton source generation in a TeO2-Bi2O3-ZnO-Na2O (TBZN) tellurite microstructured optical fiber (MOF) pumped by a 1557 nm femtosecond fiber laser. A continuous soliton wavelength shift from 1582 nm to 1851 nm was realized through a tellurite MOF as short as 6.5 cm. Experimental results are in good agreement with the numerical simulations using a generalized nonlinear SchrÖdinger equation. In addition, an analytical description of the Raman response function of tellurite glass is provided, and a Raman contribution factor of 0.51 is computed from the actual Raman gain spectrum.

Lasing properties of new Yb-doped borate compounds with varying gadolinium and yttrium concentration

Paper 7912-58 of Conference 7912
Date: Thursday, 27 January 2011
Time: 8:20 AM – 8:40 AM

Author(s): Inka B. Manek-Hönninger, Marie Chavoutier, Véronique Jubera, Dominique Descamps, Philippe Veber, Matias Velazquez, Alain Garcia, Lionel Canioni, Univ. Bordeaux 1 (France)
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We show spectroscopic and lasing properties of new ytterbium-doped borate compounds with the structure Li6[Gd(1-x)Yx]0.75Yb0.25(BO3)3 with x = 0, 0.25, 0.5, 0.75 and 1, respectively. All compounds show large emission spectra suitable for femtosecond pulse generation. We studied the laser performances in a diode-pumped linear laser cavity on 1 mm-thick crystal samples having an ytterbium doping concentration of 22 %. The compounds show all cw lasing at wavelengths around 1040 to 1060 nm with a slope efficiency of 32 %. The maximum observed output power was 460 mW at an incident pump power of 1.6 W at 972 nm.

In-vivo third-harmonic generation microscopy at 1550 nm: three-dimensional long-term time-lapse studies in living C. elegans embryos

Paper 7904-50 of Conference 7904
Date: Thursday, 27 January 2011
Time: 11:10 AM – 11:30 AM

Author(s): Rodrigo A. Aviles-Espinosa, Susana I. C. O. Santos, ICFO - Instituto de Ciencias Fotónicas (Spain); Andreas Brodschelm, Wilhelm G. Kaenders, TOPTICA Photonics AG (Germany); Cesar Alonso-Ortega, ICFO - Instituto de Ciencias Fotónicas (Spain); David Artigas-García, ICFO - Instituto de Ciencias Fotónicas (Spain) and Univ. Politècnica de Catalunya (Spain); Pablo Loza-Alvarez, ICFO - Instituto de Ciencias Fotónicas (Spain)
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In-vivo microscopic three-dimensional time-lapse studies (4D) require controlled exposure conditions to preserve sample viability. In this work, we use a 1550nm femtosecond fiber laser to obtain different tissue/structure information of living Caenorhabditis elegans embryos. By exciting Third harmonic generation at 1550nm, the emitted signal is generated at 516nm, enabling the use of standard collection optics and detectors operating near their maximum efficiency. This enables an incident power reduction allowing sample exposure for several hours. Our technique significantly reduces, sample interference (no external markers are required), demonstrating the non-invasiveness and strong potential of this particular wavelength to perform 4D studies.

Generation and amplification of 350 fs, 2 ตm pulses in Tm:fiber

Paper 7914-57 of Conference 7914
Date: Thursday, 27 January 2011
Time: 11:40 AM – 12:00 PM

Author(s): Robert A. Sims, Pankaj Kadwani, Lawrence Shah, Martin C. Richardson, CREOL, The College of Optics and Photonics, Univ. of Central Florida (United States)
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We describe the generation and amplification of femtosecond 2 ตm pulses in Tm:fiber. Mode-locked pulses at ~ 2 ตm were generated in a Tm:fiber oscillator using a single-walled carbon nanotube saturable absorber. A ring cavity was core pumped at 1.55 ตm and stable mode-locking was achieved at a repetition rate of 87 MHz. Pulses exhibited energies of 40 pJ and spectral bandwidths ~12 nm. Autocorrelation pulse width measurements indicated bandwidth limited pulses of ~350 fs duration. This oscillator was used to seed a Tm:fiber amplifier with either free space or fiber coupling. Effects of dispersion and pulse amplification are reported.

Ultrafast density- and temperature-dependent carrier dynamics in a quantum dots-in-a-well heterostructure

Paper 7937-6 of Conference 7937
Date: Sunday, 23 January 2011
Time: 11:10 AM – 11:35 AM

Author(s): Rohit P. Prasankumar, Los Alamos National Lab. (United States); Rajeev V. Shenoi, The Univ. of New Mexico (United States); Junji Urayama, Weng W. Chow, Sandia National Labs. (United States); Sanjay Krishna, The Univ. of New Mexico (United States); Antoinette J. Taylor, Los Alamos National Lab. (United States)
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The incorporation of semiconductor quantum dots into different heterostructures for applications in nanoscale photodetection and lasing is an active area of research. Here, we use ultrafast differential transmission (DT) spectroscopy to temporally and spectrally resolve density-and-temperature-dependent carrier dynamics in a quantum dots-in-a-well (DWELL) heterostructure. Our experiments provide essential insight into carrier relaxation across multiple spatial dimensions and reveal the influence of Coulomb interactions across different time scales and excitation densities. This is highlighted by the observed influence of the quantum well population upon light absorption at the quantum dot excited state, which has important implications for DWELL-based lasers and amplifiers.

Fundamentals and industrial applications of ultrashort pulsed lasers at Bosch

Paper 7920-32 of Conference 7920
Date: Tuesday, 25 January 2011
Time: 8:00 AM – 8:30 AM

Author(s): Jens Koenig, Thorsten Bauer, Robert Bosch GmbH (Germany)
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Fundamental results of ablation processes at irradiance of metals with ultrashort laser pulses in the far fluence regime are shown and discussed. Time-resolved measurements of the plasma transmission exhibit two distinctive minima. The minima in the first nanoseconds can be attributed to electrons and sublimated mass emitted from the target surface, while a following minimum after several 10 ns is due to particles and droplets after a thermal boiling process. Furthermore industrial applications of ultrashort pulsed laser ablation in the Bosch Group are shown, especially for production of exhaust gas sensors and common rail diesel systems.

Fundamentals and industrial applications of ultrashort pulsed lasers at Bosch

Paper 7925-32 of Conference 7925
Date: Tuesday, 25 January 2011
Time: 8:00 AM – 8:30 AM

Author(s): Jens Koenig, Thorsten Bauer, Robert Bosch GmbH (Germany)
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Fundamental results of ablation processes at irradiance of metals with ultrashort laser pulses in the far fluence regime are shown and discussed. Time-resolved measurements of the plasma transmission exhibit two distinctive minima. The minima in the first nanoseconds can be attributed to electrons and sublimated mass emitted from the target surface, while a following minimum after several 10 ns is due to particles and droplets after a thermal boiling process. Furthermore industrial applications of ultrashort pulsed laser ablation in the Bosch Group are shown, especially for production of exhaust gas sensors and common rail diesel systems.

Yb-doped ultrafast solid state lasers

Paper 7912-27 of Conference 7912
Date: Tuesday, 25 January 2011
Time: 10:20 AM – 10:50 AM

Author(s): Frédéric Druon, Patrick Georges, Institut d'Optique Graduate School (France)
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Ultrafast carrier and phonon dynamics in graphene: relaxation, recombination, and transport

Paper 7937-61 of Conference 7937
Date: Wednesday, 26 January 2011
Time: 1:25 PM – 1:50 PM

Author(s): Farhan Rana, Haining Wang, Jared H. Strait, Cornell Univ. (United States)
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In this talk we discuss our experimental and theoretical results on the ultrafast dynamics of carriers and phonons in graphene. Ultrafast optical and terahertz spectroscopy results show that photoexcited carriers in graphene exhibit multiple time scales while undergoing relaxation and recombination dynamics. Hot carriers lose most of their energy to optical phonons within few hundred femtoseconds resulting in a hot phonon population which then becomes the main bottleneck for carrier cooling. Hot optical phonons decay into acoustic phonons via anharmonic processes within a few picoseconds. We will discuss the relevance of our experimental and theoretical results to graphene based optoelectronics.

Measuring extremely complex ultrashort pulses with time-bandwidth products exceeding 65,000 using multiple-delay crossed-beam spectral interferometry

Paper 7950-10 of Conference 7950
Date: Wednesday, 26 January 2011
Time: 2:20 PM – 2:40 PM

Author(s): Jacob Cohen, Georgia Institute of Technology (United States); Pamela Bowlan, Swamp Optics, LLC (United States); Vikrant Chauhan, Rick Trebino, Peter M. Vaughan, Georgia Institute of Technology (United States)
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We measure the complete electric field of extremely complex ultrafast waveforms using the simple linear-optical, interferometric pulse-measurement technique, MUD TADPOLE. MUD TADPOLE is a variation of spectral interferometry that temporally interleaves both the intensity and phase of complex pulses resulting in ~fs temporal resolution and many-ns temporal range. As a result, it overcomes the spectral and temporal limitations associated with other techniques. In this paper, the waveforms were measured with ~40 fs temporal resolution over a temporal range of ~3.5ns and had time-bandwidth products exceeding 65,000. The approach is general and could allow the measurement of arbitrary optical waveforms.

Ultrafast carrier capture and THz resonances in InGaAs quantum posts

Paper 7937-2 of Conference 7937
Date: Sunday, 23 January 2011
Time: 9:10 AM – 9:35 AM

Author(s): Dominik Stehr, Univ. of California, Santa Barbara (United States) and Forschungszentrum Dresden-Rossendorf e.V. (Germany); Christopher M. Morris, Univ. of California, Santa Barbara (United States); Diyar Talbalyev, Los Alamos National Lab. (United States); Martin Wagner, Forschungszentrum Dresden-Rossendorf e.V. (Germany); Hyochul Kim, Univ. of California, Santa Barbara (United States); Antoinette J. Taylor, Los Alamos National Lab. (United States); Harald Schneider, Forschungszentrum Dresden-Rossendorf e.V. (Germany); Pierre M. Petroff, Mark S. Sherwin, Univ. of California, Santa Barbara (United States)
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Semiconductor quantum posts - nanowire-like InGaAs heterostructures in a GaAs matrix - were investigated with respect to their carrier capture dynamics after photoexcitation into the GaAs matrix. The results of the THz experiment demonstrate that after ultrafast excitation, electrons relax within a few picoseconds into the quantum posts, which act as efficient traps. Saturation of the quantum post states, probed by time-resolved photoluminescence, was reached at approximately ten times the quantum post density. Additionally, possible electronic THz resonances with a dipole moment in the growth direction were probed showing a broad response around 1.5 THz.

Ultrafast laser induced condensation of molecules

Paper 7925-2 of Conference 7925
Date: Sunday, 23 January 2011
Time: 9:20 AM – 9:40 AM

Author(s): Ling Gu, Samarendra K. Mohanty, The Univ. of Texas at Arlington (United States)
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We have found that ultrafast laser microbeam induced bubble can lead to condensation of fluorescent dye and antibodies in solution. Fluorescence imaging revealed that cavitation bubbles created high-concentration regions of dye or dye-labeled antibodies in the aqueous solution. Though, the nuclear staining propidium iodide (PI) gives order of magnitude higher fluorescence upon binding to DNA, the fluorescence of PI at the condensed spot outside cell was found to be higher than that in the nucleus. This implied concentration of PI to be increased by at least 20 times due to ultrafast laser assisted bubble formation. However, the fluorescence emission peak was found to be shifted towards the green region with even higher excitability under blue excitation. This is in contrast to the natural excitation (green) and emission (red) spectral characteristics of DNA-bound PI.

Ultrafast conditional carrier dynamics in semiconductor quantum dots

Paper 7937-3 of Conference 7937
Date: Sunday, 23 January 2011
Time: 9:35 AM – 10:00 AM

Author(s): Paola Borri, Wolfgang Langbein, Cardiff Univ. (United Kingdom)
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We provide direct evidence that the macroscopic response of the gain dynamics in electrically-pumped InGaAs/GaAs QDs is a superposition of intradot relaxation dynamics from microstates with discrete carrier numbers. The gain recovery in the presence of an optical pre-pump fully depleting the ground-state gain is measured to be faster than without pre-pump. This effect, opposite to expectations from rate equations with mean-field carrier distributions, is due to a conditional gain recovery in which microstates with slow internal dynamics are suppressed by the pre-pump. The effect is evident at 15K and still observable at 300K, beneficial for high-speed optical signal processing.

Time resolved spectroscopy on quantum dots and graphene at the FELBE free-electron laser

Paper 7937-7 of Conference 7937
Date: Sunday, 23 January 2011
Time: 11:35 AM – 12:00 PM

Author(s): Stephan F. Winnerl, Dominik Stehr, Harald Schneider, Manfred Helm, Wolfgang Seidel, Peter Michel, Forschungszentrum Dresden-Rossendorf e.V. (Germany); Evgeny Zibik, Ben Carpenter, Nathan Porter, Maurice S. Skolnick, Luke R. Wilson, The Univ. of Sheffield (United Kingdom); Thomas Grange, Robson Ferreira, Gerald Bastard, Ecole Normale Supérieure (France); Milan Orlita, Paulina Plochocka, Piotr Kossacki, Marek Potemski, Grenoble High Magnetic Field Lab. (France); Mike Sprinkle, Clair Berger, Walt de Heer, Georgia Institute of Technology (United States)
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The relaxation dynamics in self-assembled quantum dots as well as in graphene is studied by pump probe experiments using the free-electron laser FELBE at the Forschungszentrum Dresden-Rossendorf. This laser provides picosecond radiation pulses in the wavelength range 5 - 280 ตm. For the quantum dots long relaxation times (1.5 ns) are found for level separations of 14 meV (3.4 THz), decreasing very strongly to 2 ps at 30 meV (7 THz), in very good agreement with our microscopic theory of the carrier relaxation process. For graphene relaxation times ~ 20 ps are observed for excitations below the optical phonon energy.

Ultrafast optical control of terahertz surface plasmons in subwavelength hole-arrays at room temperature

Paper 7937-10 of Conference 7937
Date: Sunday, 23 January 2011
Time: 1:55 PM – 2:20 PM

Author(s): Abul K. Azad, Los Alamos National Lab. (United States)
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Ultrafast switching or modulation of the resonant behavior of the 2-D metallic arrays in terahertz frequencies is of particular interest for high speed communication and sensing applications. We demonstrate optical control of surface plasmon enhanced resonant terahertz transmission in two-dimensional subwavelength metallic hole arrays fabricated on gallium arsenide based substrates. Optically pumping the arrays creates a conductive layer in the substrate reducing the terahertz transmission amplitude of both the resonant mode and the direct transmission. Under low optical fluence, the terahertz transmission is more greatly affected by resonance damping than by propagation loss in the substrate. An ErAs:GaAs nanoisland superlattice substrate is shown to allow ultrafast control with a switching recovery time of ~10 ps.

Near-field enhancement in plasmonic laser nanoablation using gold nanorods on a silicon substrate

Paper 7925-12 of Conference 7925
Date: Sunday, 23 January 2011
Time: 2:20 PM – 2:40 PM

Author(s): Richard K. Harrison, Adela Ben-Yakar, The Univ. of Texas at Austin (United States)
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We studied ultrafast plasmonic laser nanoablation (PLN) of silicon using gold nanorods using both experiments and numerical simulations. We fabricated isolated features on a silicon surface as small as the dimensions of the nanorods used in the study - 25 nm x 75 nm. We compare the shape, depth and fluence observed at experimental nanorod ablation sites with the distribution, localization, and near-field enhancement magnitude observed from calculated electromagnetic fields. From this data, we conclude that the Poynting vector magnitude is a better predictor of ablation size, shape and threshold for ultrafast PLN than the square of the electric field.

Semiconductor plasmons for THz frequency plasmonics

Paper 7937-12 of Conference 7937
Date: Sunday, 23 January 2011
Time: 2:35 PM – 3:00 PM

Author(s): Euan Hendry, The Univ. of Exeter (United Kingdom)
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Surface plasmons (SPs) are electromagnetic waves that propagate along the interface between a conductor and insulator. To date, studies of SPs have been limited to optical frequencies near metallic plasma frequencies, where SP modes are strongly confined to metal surfaces. However, we have shown that certain semiconductors can support confined SPs at THz frequencies. We have demonstrated that SPs play an important role in a variety of physical phenomena, elucidating their role in the transmission of THz radiation through semiconductor structures such as sub-wavelength slits and holes.

Time-gated spontaneous and resonance Raman spectroscopy for biomedical applications

Paper 7902-32 of Conference 7902
Date: Sunday, 23 January 2011
Time: 3:10 PM – 3:30 PM

Author(s): Zachary J. Smith, Florian Knorr, Cynthia V. Pagba, Sebastian Wachsmann-Hogiu, UC Davis Medical Ctr. (United States)
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Raman scattering is a technique that has high chemical specificity. However, Raman scattering is a weak process often overshadowed by a strong fluorescence background. One way to reject the fluorescence signal in Raman measurements is by using an ultrafast shutter. Previous attempts used lasers at low rep rate and damagingly high pulse energies. Here we present a shutter that utilizes nanojoule level pulse energies and 80 MHz rep rates, below the nonthermal ablation threshold, and average powers low enough to avoid thermal damage. We will show fluorescence free Raman spectra obtained from highly fluorescent biological and nonbiological samples.

Ultrafast photoconductors based on subwavelength metallic gratings for the next generation of photoconductive terahertz sources

Paper 7937-14 of Conference 7937
Date: Sunday, 23 January 2011
Time: 3:15 PM – 3:30 PM

Author(s): Christopher W. Berry, Mona Jarrahi, Univ. of Michigan (United States)
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We present a new generation of ultrafast and high quantum efficiency photoconductors fabricated on high quality crystalline semiconductors. The device consists of a metal-semiconductor-metal photoconductor with a subwavelength contact electrode grating at the optical pump wavelength. Ultrafast photocurrent impulse response and high quantum efficiency operation is achieved through the excitation of surface plasmon waves, which significantly enhance the concentration of photo-generated carriers in close proximity to photoconductor contact electrodes. Ultrafast photocurrent impulse response times as low as 100fs FWHM are estimated for the presented photoconductors, which are faster than the photocurrent response of previously demonstrated photoconductors with short carrier lifetime semiconductors.

Basic mechanisms of the femtosecond laser interaction with a plasmonic nanostructure in water

Paper 7925-15 of Conference 7925
Date: Sunday, 23 January 2011
Time: 3:50 PM – 4:10 PM

Author(s): Michel Meunier, Étienne Boulais, Rémi Lachaine, Charles-André Caron, Ecole Polytechnique de Montréal (Canada)
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The irradiation of a plasmonic nanostructure embedded in a biological media by a femtosecond laser could results in a highly localized plasma and heat production yielding to the generation of cavitation bubbles and nanosurgery of cells. To understand the basic mechanisms underlying this process, a combination of simulation work and experimental measurement is used to study the formation of cavitation bubbles and the generation of strong pressure waves in the medium following the irradiation of plasmonic nanostructures in a water solution. Influence of laser parameters such as pulse duration, wavelength and fluence is discussed.

Latest advances in ultra-fast laser sources for multiphoton microscopy

Paper 7903-19 of Conference 7903
Date: Sunday, 23 January 2011
Time: 3:50 PM – 4:05 PM

Author(s): Philip G. Smith, Spectra-Physicsฎ, a Newport Corp. Brand (United States)
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The advent of compact, fully automated, and widely wavelength-tunable ultrafast oscillators has triggered an explosive growth in their use in a broad array of multiphoton imaging techniques. Over the past decade laser manufacturers have constantly improved the performance characteristics of these sources to meet the requirements of the user community. We will review the latest advances at Newport / Spectra-Physics in this field and discuss new ways of optimizing key parameters for efficient deep-tissue fluorescence generation, including turn-key, automated second order dispersion compensation that allows for optimization of the pulse width at the sample over a wide wavelength range, without compromising beam pointing and other critical beam parameters.

Plasmon-enhanced ultrafast laser cell transfection

Paper 7911-17 of Conference 7911
Date: Sunday, 23 January 2011
Time: 3:50 PM – 4:10 PM

Author(s): Eric D. Diebold, Harvard Univ. (United States); Andrew Koh, Stanford Univ. School of Medicine (United States); Paul Peng, Valeria Nuzzo, Harvard Univ. (United States); Alexander Heisterkamp, Laser Zentrum Hannover e.V. (Germany); Eric Mazur, Harvard Univ. (United States)
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We present a method for transfecting biological cells using ultrafast plasmons excited on large areas of bio-compatible, nano-pyramid substrates. This technique does not employ any potentially toxic chemical transfection reagents or metallic nanoparticles. Leveraging the field enhancement supported by these pyramidal plasmonic nanostructures, we generate localized, transient pores in the membranes of large numbers of cells at a rate of approximately 104 per second. Diffusion through these pores enables the delivery of functional short interfering RNA (siRNA) molecules into the cells. We demonstrate both cellular uptake of biomolecules and cell transfection after plasmon-enhanced laser cell perforation.

Ultrafast energy transfer between water molecules

Paper 7937-17 of Conference 7937
Date: Sunday, 23 January 2011
Time: 4:50 PM – 5:15 PM

Author(s): Till N. Jahnke, Johann Wolfgang Goethe-Univ. Frankfurt am Main (Germany)
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The talk will present an introduction to the phenomenon of Interatomic Coulombic Decay and the experimental technique of COLTRIMS that was employed to identify its occurrence. Apart from the case of water dimers two more benchmark experiments showing unveiling that ultrafast interatomic decay mechanism will be presented.

From multi kW continuous wave to multi MW femtosecond pulses: recent developments exploiting disk laser technology

Paper 7912-8 of Conference 7912
Date: Monday, 24 January 2011
Time: 8:50 AM – 9:10 AM

Author(s): Sascha Weiler, Marco Holzer, TRUMPF Laser- und Systemtechnik GmbH (Germany)
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Disk lasers combine high efficiency, excellent beam quality, high average and/or peak power with moderate cost and high reliability at multiple wavelengths, ranging from the infrared over the green to the ultraviolet. The demonstrated infrared average powers range from tens of kW in CW operation over >1 kW in ns pulses to >100 W in ps pulses and > 70 W in fs pulses. Wavelength conversion for nearly all modes of operation, e.g. 700 W@515nm in ns pulses, enlarges the fields of applications, making the disk technology today's most versatile laser platform.

Ultrafast dynamics of femtosecond laser-induced nanostructure formation on metals

Paper 7937-22 of Conference 7937
Date: Monday, 24 January 2011
Time: 9:15 AM – 9:40 AM

Author(s): Chunlei Guo, Univ. of Rochester (United States)
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In this talk, I will discuss our recent study on femtosecond laser-induced nanostructures on metals. We found that nanostructure formation can vary greatly among different metals, and the differences are attributed to the competition of ultrafast processes involved, including electron-phonon coupling and hot electron diffusion, following femtosecond laser heating of metals.

Tip-enhanced ultrafast spectroscopy and microscopy of organic solar cell blend film

Paper 7937-23 of Conference 7937
Date: Monday, 24 January 2011
Time: 9:40 AM – 10:05 AM

Author(s): Alfred J. Meixner, Dai Zhang, Eberhard Karls Univ. Tübingen (Germany)
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Poly(3-hexylthiophene) (P3HT) and [6, 6]-penyl-C61 butyric acid methyl ester (PCBM) are widely employed in the field of organic solar cells as the electronic donors and acceptors. The exciton creation, dissociation and separated charge transportation in the P3HT and PCBM blends are critical for achieving a high performance of the solar cells. To investigate the excition diffusion and dissociation, both high spatial resolution and ultrafast optical techniques are required. We will report about our progress in combining our parabolic mirror assisted tip-enhanced near-field optical microscope with an ultrafast laser system and report about nonlinear excitation behavior of inverted tip antennae.

Carrier dynamics investigation in quantum cascade lasers using ultrafast pulses

Paper 7937-25 of Conference 7937
Date: Monday, 24 January 2011
Time: 11:00 AM – 11:15 AM

Author(s): Sheng Liu, Elaine Lalanne, Robinson A. Kuis, Anthony M. Johnson, Univ. of Maryland, Baltimore County (United States)
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We employ femtosecond Mid-IR time-resolved pump-probe technique to investigate the nature of carrier transport in QCLs. Gain recovery and amplification of probe pulses are observed near threshold and at low bias, respectively. This is due to the interaction between strong pump pulses and electrons, which reveals the population difference between upper and lower lasing states. When biased near threshold, following a fast (shorter than 200fs) gain recovery, oscillation of the probe signal is observed within the first picosecond. This oscillation can not be seen when pump power is attenuated. Slower gain recovery with lifetime of 3-4ps is later seen.

Synchronized picosecond pulses at two different wavelengths from a compact fiber laser source for Raman microscopy

Paper 7903-32 of Conference 7903
Date: Monday, 24 January 2011
Time: 11:25 AM – 11:45 AM

Author(s): Khanh Q. Kieu, Nasser Peyghambarian, College of Optical Sciences, The Univ. of Arizona (United States)
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We report on the development of a fiber laser system that supplies synchronized picosecond pulses at two different wavelengths suitable for Raman microscopy

Passively mode-locked two section laser diode with intracavity dispersion control

Paper 7937-27 of Conference 7937
Date: Monday, 24 January 2011
Time: 11:40 AM – 11:55 AM

Author(s): Tobias Schlauch, Jan Balzer, Martin R. Hofmann, Ruhr-Univ. Bochum (Germany); Andreas Klehr, Götz Erbert, Günther Tränkle, Ferdinand-Braun-Institut für Höchstfrequenztechnik (Germany)
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The generation of ultrashort laser pulses with compact semiconductor based sources is extremely interesting for many applications like communication technology, material processing or ultrafast spectroscopy. We investigate the intracavity and extracavity dispersion management of a passively mode-locked laser diode in Fourier transform external cavity laser (FTECAL) geometry. Via SHG-FROG measurements we analyze the influence of manipulations of the intracavity dispersion on the chirp of the emitted pulses and demonstrate the generation of 200 fs pulses by a combination of intracavity dispersion management with external pulse compression.

x-vivo ultra-high-resolution optical coherence tomography imaging of fine lung structure by use of a high-power Gaussian-like supercontinuum at 0.8-um wavelength

Paper 7893-34 of Conference 7893
Date: Monday, 24 January 2011
Time: 12:10 PM – 12:30 PM

Author(s): Norihiko Nishizawa, Shutaro Ishida, Nagoya Univ. (Japan); Takefumi Ohta, Kazuyoshi Itoh, Osaka Univ. (Japan); Masashi Kitatsuji, Hiroyoshi Ohshima, HOYA Corp. (Japan); Miyoko Matsushima, Tsutomu Kawabe, Nagoya Univ. (Japan)
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Ex vivo cross-sectional imaging of isolated rat lungs was demonstrated using UHR-OCT. A 120 nm-wide, high-power, Gaussian-like supercontinuum was generated at wavelength of 0.8 um region and it was used as the light source in time domain UHR-OCT. An ultrahigh resolution of 2.1 um in tissue was obtained and the achieved sensitivity was 105 dB. The detailed structures of the trachea, visceral pleura, and alveoli were observed clearly. When saline was instilled into the lung, the penetration depth was improved, and clear images of the fine structure of the lung, including alveoli, were observed owing to the index matching effect.

Triply surface-plasmon resonant four-wave mixing imaging of gold nanoparticles

Paper 7911-33 of Conference 7911
Date: Monday, 24 January 2011
Time: 1:30 PM – 1:50 PM

Author(s): Francesco Masia, Wolfgang Langbein, Peter Watson, Paola Borri, Cardiff Univ. (United Kingdom)
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We demonstrate a novel multiphoton microscopy technique not relying on (hence not limited by) fluorescence emission, which exploits four-wave mixing (FWM) of gold nanoparticles (GNPs) in resonance with their surface Plasmon. The coherent, transient and resonant nature of this signal allows its detection free from the background limiting other contrast methods for GNPs. We show high-contrast high-resolution imaging of gold-labels down to 5nm size in Golgi structures of HepG2 cells. We also show sensitivity to single GNPs. By detecting the transient nonlinearity using 100fs pulses with adjustable delay we gain fundamental insights into the physical processes creating FWM.

Ultrafast generation of injection currents in semiconductor quantum wells

Paper 7937-29 of Conference 7937
Date: Monday, 24 January 2011
Time: 1:30 PM – 1:55 PM

Author(s): Torsten Meier, Huynh Thanh Duc, Jens Förstner, Univ. Paderborn (Germany); Shekhar Priyadarshi, Ana Maria Racu, Klaus Pierz, Uwe Siegner, Mark Bieler, Physikalisch-Technische Bundesanstalt (Germany)
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The generation of injection currents in GaAs quantum well systems is investigated experimentally and theoretically. In the experiments, the radiation emitted due to the charge current transients is detected. The measured signals are compared to a microscopic theory that uses multisubband semiconductor Bloch equations which are set up in the basis of 14x14 band k.p calculations. Our combined experimental and theoretical analysis shows that the obtained oscillatory dependence of the injection current amplitude and direction on the exciting photon energy is caused by the coupling of the light- and heavy-hole bands.

CPA-free picosecond fiber amplifier with >10ตJ pulse energy and >300kW peak power

Paper 7925-27 of Conference 7925
Date: Monday, 24 January 2011
Time: 1:40 PM – 2:00 PM

Author(s): Yoann Zaouter, Maxime Lebugle, Franck Morin, Eric Mottay, Clemens Hönninger, Amplitude Systemes (France)
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We demonstrate a compact and robust picosecond fiber amplifier system that produces >10uJ pulse energy and average powers exceeding 10W while maintaining a narrow spectral bandwidth. This simple and compact CPA-free fiber amplifier system is well suited for micro-machining applications as well as for scientific applications that require narrow optical spectra as e.g. CARS spectroscopy.

Recent advances in electrically pumped VECSELs for modelocking

Paper 7919-17 of Conference 7919
Date: Monday, 24 January 2011
Time: 4:45 PM – 5:15 PM

Author(s): Yohan Barbarin, ETH Zurich (Switzerland)
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Passively modelocked vertical external cavity surface emitting lasers (VECSELs) have generated shorter pulses and higher average powers than any other modelocked semiconductor laser using optical pumping (135-fs at 35-mW and 2.1-W in 4.7-ps pulses). Electrical pumping (EP) of VECSELs is the clear next step for compact high power ultrafast laser sources. Since the impressive performance in continuous wave of the EP-VECSEL of Novalux, very few EP-VECSELs results have been reported. We discuss EP-VECSEL designs suitable for modelocking. They require an optimized balance between electrical resistance, optical losses, dispersion and cw output power. Initial EP-VECSEL devices generate >100-mW cw power.

Ultrafast photoacoustic imaging with improved elevational focusing

Paper 7899-54 of Conference 7899
Date: Monday, 24 January 2011
Time: 5:00 PM – 5:15 PM

Author(s): Yu-Hsin Wang, Pai-Chi Li, National Taiwan Univ. (Taiwan)
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Conventional photoacoustic imaging system has limited temporal resolution and hence prohibits the applications in areas such as real-time 3D imaging. In this study, an ultrafast photoacoustic imaging system with its frame rate up to 2,000Hz is demonstrated. An ultrasound transducer with plane wave excitation and a high pulse repetition rate laser are utilized to acquire the data in parallel. Additionally, the 3D data acquisition which approaches the video rate is achieved when the volume data are collected by swept scanning of a motor. The synthetic aperture focusing technique (SAFT) based on the concept of the virtual source in the elevation plane is applied to improve the imaging quality. The 3D imaging has a frame rate of 12Hz to cover a square region of 19.2mm × 19.2mm.

Yb-doped ultrafast thin disk lasers

Paper 7912-22 of Conference 7912
Date: Tuesday, 25 January 2011
Time: 8:00 AM – 8:30 AM

Author(s): Thomas Südmeyer, Cyrill Bär, ETH Zurich (Switzerland); Christian Kränkel, ETH Zurich (Switzerland) and Univ. Hamburg (Germany); Clara J. Saraceno, Oliver H. Heckl, Matthias C. Golling, ETH Zurich (Switzerland); Rigo Peters, K. Petermann, Guenter Huber, Univ. Hamburg (Germany); Ursula Keller, ETH Zurich (Switzerland)
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Ultrafast thin disk lasers achieve higher pulse energies and average power levels than any other modelocked oscillators. The key components of SESAM modelocked thin disk lasers are used in reflection, which is an advantage for the generation of ultrashort pulses with excellent temporal, spectral and spatial properties. We review the development and report latest results. We report on successful scaling of a Yb:Lu2O3 thin disk laser to 141 W average power, setting a new record for mode-locked laser oscillators. Such performance is important for a growing number of applications such as material processing or driving experiments in high field science.

Highly flexible ultrafast laser system with 220W average power

Paper 7912-23 of Conference 7912
Date: Tuesday, 25 January 2011
Time: 8:30 AM – 8:50 AM

Author(s): Torsten G. Mans, Jan Dolkemeyer, AMPHOS GmbH (Germany); Peter Russbueldt, Fraunhofer-Institut für Lasertechnik (Germany); Claus Schnitzler, AMPHOS GmbH (Germany)
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We present a flexible ultrafast laser amplifier system based on InnoSlab technology with an average power exceeding 200W. The pulse duration of the system can be continuously tuned between 530fs and 5.4ps limited by the amplification bandwidth of Yb:YAG and the currently used seed source. The repetition rate can be varied from 26.6MHz down to 1MHz. Without the need of compression of the high power beam some 10ตJ are accessible before first signs of self-phase modulation avoid operation with low spectral bandwidth (<3nm) close to the transform limit. Beam quality is measured to be near the diffraction limit (M2<=1.3).

Industrial production with ultra fast laser workstations

Paper 7925-18 of Conference 7925
Date: Tuesday, 25 January 2011
Time: 9:40 AM – 10:00 AM

Author(s): Eric Audouard, Univ. Jean Monnet Saint-Etienne (France); Hervé Soder, Impulsion SAS (France)
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In this work, we will underline some practical applications and the link between a better knowledge of physical mechanisms and the development of industrial processes. Of course, we have to pay attention to typical parameters of industrial development, such as the processing time. For instance, the physical time can be easily calculated, using the total length of the machining, speed and laser parameters. This calculated physical process time can be compared to the effective time needed to machine the sample. Femtosecond technology has now proven its capacity to lead innovative production, even if it's still in some well defined fields, but its contribution is non negligible in a context of economical crisis.

Industrial production with ultra fast laser workstations

Paper 7920-18 of Conference 7920
Date: Tuesday, 25 January 2011
Time: 9:40 AM – 10:00 AM

Author(s): Eric Audouard, Univ. Jean Monnet Saint-Etienne (France); Hervé Soder, Impulsion SAS (France)
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In this work, we will underline some practical applications and the link between a better knowledge of physical mechanisms and the development of industrial processes. Of course, we have to pay attention to typical parameters of industrial development, such as the processing time. For instance, the physical time can be easily calculated, using the total length of the machining, speed and laser parameters. This calculated physical process time can be compared to the effective time needed to machine the sample. Femtosecond technology has now proven its capacity to lead innovative production, even if it's still in some well defined fields, but its contribution is non negligible in a context of economical crisis.

Femtosecond pump-probe imaging reveals chemical and architectural changes in human melanoma

Paper 7903-61 of Conference 7903
Date: Tuesday, 25 January 2011
Time: 9:55 AM – 10:10 AM

Author(s): Thomas E. Matthews, Ivan Piletic, Maria Angelica Selim, Mary Jane Simpson, Warren S. Warren, Sr., Duke Univ. (United States)
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We have developed a nonlinear imaging method, based on pump-probe spectroscopy in a scanning laser microscope, to directly discriminate and image the two varieties of melanin found in human skin: eumelanin and pheomelanin. We imaged a variety of excised pigmented lesions including benign nevi, compound and dysplastic nevi, malignant melanomas and pigmented basal cell carcinomas. It was found that the melanin in melanomas and carcinomas was predominantly eumelanin, while the surrounding normal tissue and benign lesions were more pheomelanic. We extended this technique to H&E stained slides, allowing co-localization with structural features and making it compatible with traditional pathology samples.

1100W Yb:YAG fs INNOSLAB amplifier

Paper 7912-28 of Conference 7912
Date: Tuesday, 25 January 2011
Time: 10:50 AM – 11:20 AM

Author(s): Peter Russbueldt, Fraunhofer-Institut für Lasertechnik (Germany); Torsten G. Mans, RWTH Aachen (Germany); Hans-Dieter Hoffmann, Reinhart Poprawe, Fraunhofer-Institut für Lasertechnik (Germany)
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To transfer femtosecond technology to industrial applications, laser sources of high average power are essential. We demonstrate a compact diode-pumped Yb:KGW femtosecond oscillator - Yb:YAG Innoslab amplifier MOPA with nearly transform and diffraction limited 636 fs pulses at 620 W average output power and 20 MHz repetition rate. By cascading two amplifiers an average output power of 1.1 kW and peak power of 80 MW is achieved in a single, linearly polarized beam. The MOPA is operated at room temperature and no CPA technique is used. The specific properties of Innoslab MOPAs are compared with fibers and thin-disks.

Time-resolved x-ray scattering

Paper 7937-40 of Conference 7937
Date: Tuesday, 25 January 2011
Time: 11:10 AM – 11:35 AM

Author(s): Matias Bargheer, Univ. Potsdam (Germany)
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Ultrafast x-ray diffraction has become more and more prevalent in various scientific disciplines that are interested in directly observing atomic motion in real time. The timescale, amplitude and phase of collective atomic motion can be determined with high accuracy, even when the induced amplitude is smaller than thermal fluctuations. The structural rearrangements induced by an ultrafast stimulus (charge carriers excited or heat deposited by a laser pulse) can be recorded in real time. This yields additional information of physical properties such as the electron-phonon or spin-lattice interaction. We discuss examples including the direct observation of indirect magneto-electric coupling in oxides.

Short pulse and high repetition rate diode-pumped Yb:CaF2 regenerative amplifier

Paper 7912-29 of Conference 7912
Date: Tuesday, 25 January 2011
Time: 11:20 AM – 11:40 AM

Author(s): Sandrine Ricaud, Amplitude Systemes (France) and Lab. Charles Fabry (France); Frédéric Druon, Institut d'Optique Graduate School (France); Dimitris N. Papadopoulos, Lab. Charles Fabry (France); Patrice Camy, Jean-Louis Doualan, Richard Moncorgé, ENSICAEN (France); Martin Delaigue, Antoine Courjaud, Yoann Zaouter, Amplitude Systemes (France); Patrick Georges, Institut d'Optique Graduate School (France); Eric Mottay, Amplitude Systemes (France)
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We report a diode-pumped regenerative amplifier based on an Yb:CaF2 crystal, producing short pulses for repetition rates between 100 Hz and 10 kHz. The seed pulses are generated by an Yb:CALGO oscillator with a FWHM bandwidth of 15 nm. The shortest pulses duration generated is 178 fs with a corresponding energy of 1.4 mJ before compression, at a repetition rate of 500 Hz. At higher repetition rate, we obtained up to 1.4W of average power before compression, and we also observed that the pulse duration tends to increase above 1 kHz, reaching 400 fs at 10 kHz.

QD-based saturable absorbers for ultrafast lasers

Paper 7919-29 of Conference 7919
Date: Tuesday, 25 January 2011
Time: 11:30 AM – 12:00 PM

Author(s): Edik U. Rafailov, Svetlana A. Zolotovskaya, Mantas Butkus, Univ. of Dundee (United Kingdom)
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Novel materials, notably quantum-dot (QD) semiconductor structures offer the unique possibility of combining exploitable spectral broadening of both gain and absorption with ultrafast carrier dynamic properties. Thanks to these characteristics QD-based devices have enhanced the properties of ultrashort pulse lasers and opened up new possibilities in ultrafast science and technology. In this paper we review the recent progress on the development of novel quantum-dot SESAM structures for different lasers. We also demonstrate that QD structures can be designed to provide compact and efficient ultrashort pulse laser sources with high and low repetition rates.

Trends in nanoplasmonics: ultrasmall, ultrafast, ultrastrong

Paper 7937-42 of Conference 7937
Date: Tuesday, 25 January 2011
Time: 1:30 PM – 1:55 PM

Author(s): Mark I. Stockman, Georgia State Univ. (United States)
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Nanoplasmonics deals with collective electron dynamics on the surface of metal nanostructures, which arises as a result of excitations called surface plasmons. The surface plasmons localize and concentrate optical energy in nanoscopic regions creating highly enhanced local optical fields. They undergo ultrafast dynamics with timescales as short as a few hundred attoseconds. From the latest developments and original work in nanoplasmonics, we will consider SPASER (quantum nanoscale optical generator and ultrafast amplifier), ultrafast coherent control on the nanoscale, generation of EUV radiation by plasmonic enhancement, adiabatic nano-concentration of optical energy, and SPIDER (surface-plasmon-induced drag-effect rectification) that leads to generation of nanoscale THz fields by femtosecond polaritonic pulses in metal nanowires.

Ultrafast active plasmonic coupling

Paper 7937-43 of Conference 7937
Date: Tuesday, 25 January 2011
Time: 1:55 PM – 2:20 PM

Author(s): Nir Rotenberg, Markus Betz, Jan N. Caspers, Henry M. van Driel, Univ. of Toronto (Canada)
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One of the key components of a plasmonic-based nanophotonic device for information processing is an active element, where a plasmonic signal is switched or modulated. Here, we present several approaches demonstrating active control of plasmonic coupling on picosecond time scales. Existing plasmonic coupling resonances, on gold films with grating overlayers, are spectrally shifted by the optically changing the permittivity of either the gold or the adjacent dielectric. Further, plasmonic coupling resonances are all-optically introduced on planar gold films, which show no such coupling initially; the resonant coupling window is shorter than a picosecond. These effects are characterized, both spectrally and in terms of the pump fluence.

Ultrafast microsphere near-field nanostructuring

Paper 7925-40 of Conference 7925
Date: Tuesday, 25 January 2011
Time: 3:30 PM – 3:50 PM

Author(s): Karl-Heinz Leitz, Ulf Quentin, Lehrstuhl für Photonische Technologien (Germany) and Erlangen Graduate School of Advanced Optical Technologie (Germany); Benjamin Hornung, Consultant (Germany); Andreas Otto, Ilya Alexeev, Michael Schmidt, Lehrstuhl für Photonische Technologien (Germany) and Erlangen Graduate School of Advanced Optical Technologie (Germany)
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The utilisation of non-linear multi-photon and near-field effects allows a sub-diffraction limited laser based nanostructuring. In this contribution a basic study of the influence of processing parameters on the microsphere near-field nanostructuring with ultrashort pico- and femtosecond laser pulses will be presented. The experimental and numerical results with dielectric and metal nanoparticles on dielectric, semiconductor and metal substrates show the influence of particle size and material, substrate material, pulse duration, number of contributing laser pulses and polarisation on the structuring process.

Ultrafast microsphere near-field nanostructuring

Paper 7920-40 of Conference 7920
Date: Tuesday, 25 January 2011
Time: 3:30 PM – 3:50 PM

Author(s): Karl-Heinz Leitz, Ulf Quentin, Lehrstuhl für Photonische Technologien (Germany) and Erlangen Graduate School of Advanced Optical Technologie (Germany); Benjamin Hornung, Consultant (Germany); Andreas Otto, Ilya Alexeev, Michael Schmidt, Lehrstuhl für Photonische Technologien (Germany) and Erlangen Graduate School of Advanced Optical Technologie (Germany)
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The utilisation of non-linear multi-photon and near-field effects allows a sub-diffraction limited laser based nanostructuring. In this contribution a basic study of the influence of processing parameters on the microsphere near-field nanostructuring with ultrashort pico- and femtosecond laser pulses will be presented. The experimental and numerical results with dielectric and metal nanoparticles on dielectric, semiconductor and metal substrates show the influence of particle size and material, substrate material, pulse duration, number of contributing laser pulses and polarisation on the structuring process.

Robust quantum dot state preparation via adiabatic passage with frequency-swept laser pulses

Paper 7937-47 of Conference 7937
Date: Tuesday, 25 January 2011
Time: 3:55 PM – 4:20 PM

Author(s): Xavier Marie, Institut National des Sciences Appliquées de Toulouse (France)
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We report a new experimental approach to the optical preparation of a quantum state in an individual dot, namely rapid adiabatic passage (RAP) from the ground to an excited state through excitation with laser pulses whose frequency is swept slowly across the resonance. Using these chirped pulses we are able to induce a complete and robust population transfer between quantum material states. This observation in photoluminescence experiments is made possible by introducing a novel all optical detection scheme for the resonant electron-hole pair (exciton) generation.

Femtosecond laser nanofabrication of metal structures through multiphoton photoreduction

Paper 7927-14 of Conference 7927
Date: Tuesday, 25 January 2011
Time: 4:00 PM – 4:20 PM

Author(s): Kevin Vora, SeungYeon Kang, Michael Moebius, Eric D. Mazur, Harvard Univ. (United States)
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We present an ultrafast laser technique for direct-writing gold and silver structures of tunable dimensions. By utilizing nonlinear optical interactions between chemical precursors and femtosecond pulses, we limit metal-ion photoreduction processes to focused spots smaller than that of the diffraction-limit. This creates metal nanostructures in a focal volume that can be rapidly scanned in 3D. By varying the solution chemistry and laser pulse parameters, we demonstrate morphological control of the resulting structures. We fabricate grid and woodpile patterns over hundreds of micrometers in dimensions. We show the process is scalable and possesses optical characteristics suitable for SERS or metamaterial applications.

High temperature multiparameter sensor with 1000ฐC capability

Paper 7934-13 of Conference 7934
Date: Tuesday, 25 January 2011
Time: 4:40 PM – 5:00 PM

Author(s): Robert B. Walker, Dan Grobnic, Stephen J. Mihailov, Communications Research Ctr. Canada (Canada)
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Spectral characteristics of fiber Bragg gratings are affected by both strain and temperature. While this makes gratings useful for sensing, care must be taken to ensure adequate discrimination between spectral shifts associated with strain and those due to changes in temperature. Recently, monitoring of tilted grating cladding modes has been utilized for this purpose. The drawback of presently published examples is that none offer such measurement capabilities at high temperature (800 ~ 1000 ฐC). In this paper, by exploiting the characteristics of Type II fs-IR written gratings, we present such an example. Achieving similar responsivity with significantly improved thermal durability.

Controlling ultrafast light with dispersive metamaterials

Paper 7946-29 of Conference 7946
Date: Tuesday, 25 January 2011
Time: 5:00 PM – 5:20 PM

Author(s): Dean P. Brown, UES, Inc. (United States); Augustine M. Urbas, Air Force Research Lab. (United States)
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Because metamaterials possess strong resonances, a strong group delay dispersion (GDD) is also possible, which is an important parameter for ultrafast laser pulses. A metamaterial design was optimized to create a large GDD near a central wavelength of 810nm. Then a multiphoton intrapulse interference phase scan (MIIPS) technique was used to measure the GDD directly over the bandwidth of an ultrafast laser. We found GDD values were an order of magnitude larger than for dispersive optical glass three orders of magnitude thicker. Finally, we explored ways that dispersive metamaterials can shape an ultrafast pulse of light shorter than 20fs.

Enhanced photoacoustic detection through multiple picosecond pulse excitation

Paper 7899-82 of Conference 7899
Date: Tuesday, 25 January 2011
Time: 5:00 PM – 5:15 PM

Author(s): Tan Liu, Vladislav V. Yakovlev, Hao Feng Zhang, Univ. of Wisconsin-Milwaukee (United States)
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The signal-to-noise-ratio in photoacoustic imaging is often limited by the maximum permissible exposure imposed by laser safety. We demonstrated that a train of picosecond pulses, which lasts less than the minimum of the medium's thermal relaxation time and stress relaxation time, can effectively amplify the amplitude of the induced photoacoustic wave compared with a single picosecond pulse induced photoacoustic wave. This method is especially invaluable for photoacoustic imaging based on nonlinear optical effects, such as multiple photon absorption and stimulated Raman absorption, where ultrashort, high-intensity pulses are usually required.

Generation of 30 fs pulses at 670 nm using a frequency-doubled fiber laser system and a photonic-crystal fiber with two zero-dispersion wavelengths

Paper 7914-80 of Conference 7914
Date: Tuesday, 25 January 2011
Time: 6:00 PM

Author(s): Robert Herda, Tobias Junggeburth, TOPTICA Photonics AG (Germany); Kim Per Hansen, NKT Photonics A/S (Denmark); Patrick Leisching, TOPTICA Photonics AG (Germany)
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The frequency-doubled radiation of an Erbium-doped fiber laser is used for supercontinuum generation in a small-core microstructured fiber with two zero-dispersion wavelengths. Average powers up to 49 mW are launched into the microstructured fiber. The generated supercontinuum shows a short-wavelength peak centered around 670 nm and a long-wavelength peak centered around 1100 nm. More than 35 mW is contained in the low wavelength peak. We use the anomalous dispersion of a SF10 prism compressor to compress the low wavelength peak of the spectrum. The compressed pulse has a central wavelength of 670 nm and a duration of 30 fs.


MHz-rate picosecond laser discretely tunable from the near-IR to deep UV

Paper 7917-29 of Conference 7917
Date: Wednesday, 26 January 2011
Time: 9:10 AM – 9:30 AM

Author(s): Vladislav V. Yakovlev, Univ. of Wisconsin-Milwaukee (United States)
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We demonstrated a new class of bandwidth-limited broadly tunable ultrafast laser systems based on stimulated Raman amplification of white-light continuum. Applications to resonance Raman scattering are discussed.

Helical ionizing channels generated with ultrafast interfering Bessel laser pulses

Paper 7950-11 of Conference 7950
Date: Wednesday, 26 January 2011
Time: 2:40 PM – 3:00 PM

Author(s): Nicholas Barbieri, Matthew Weidman, Matthieu Baudelet, Martin Richardson, Demetrios Christodoulides, Georgios Siviloglou, CREOL, The College of Optics and Photonics, Univ. of Central Florida (United States); Eric Johnson, Zachary Roth, The Univ. of North Carolina at Charlotte (United States)
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Using linear diffraction techniques, helical beams, which feature irradiance peaks which rotate about the optical axis with propagation, can be formed through the superposition of to oppositely charged order 1 Bessel beams. Such techniques can be extended to shape and control the propagation ultrafast laser pulses, which have sufficient irradiance to ionize air and induce laser plasma filamentation, enabling the generation of shaped ionized channels. By generating a helical beam geometry with a 12mJ femtosecond laser, ionized helical channels have been obtained in the laboratory.

Ultrafast terahertz spectroscopy of few-layer graphene

Paper 7937-64 of Conference 7937
Date: Wednesday, 26 January 2011
Time: 2:40 PM – 3:05 PM

Author(s): Hyunyong Choi, Ferenc Borondics, David A. Siegel, Shuyun Zhou, Michael C. Martin, Alessandra Lanzara, Robert A. Kaindl, Lawrence Berkeley National Lab. (United States)
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Graphene is attracting significant interest due to the unique physics of its 2D charge carriers in a linear electronic bandstructure, and due to possible applications in e.g. high-speed electronics. Here, we discuss the broadband optical conductivity and ultrafast THz dynamics of graphene in the few-layer limit. The equilibrium optical response in epitaxial graphene is consistent with the electrodynamics of a dense Dirac electron plasma, arising from highly-doped layers at the graphene-substrate interface. We will further discuss the transient THz response, which reflects the recombination dynamics and unusual Drude response of graphene and its dependence on the carrier distribution function.

Nuclear feedback in a single charged quantum dot under pulsed optical control

Paper 7948-29 of Conference 7948
Date: Wednesday, 26 January 2011
Time: 2:55 PM – 3:20 PM

Author(s): Thaddeus D. Ladd, David L. Press, Kristiaan De Greve, Peter L. McMahon, Stanford Univ. (United States); Benedikt Friess, Christian Schneider, Martin Kamp, Sven Höfling, Alfred W. B. Forchel, Julius-Maximilians-Univ. Würzburg (Germany); Yoshihisa Yamamoto, Stanford Univ. (United States)
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The control of a single electron spin in a self-assembled semiconductor quantum dot using single, ultrafast optical pulses has emerged as a promising route for high-speed, optically driven quantum information processing. Such manipulation of a single electron spin hyperfine-coupled to a nuclear ensemble has been observed to stabilize the random drift of that ensemble. This observation may enable complex sequences for dynamical decoupling and assist in scaling to multiple-qubit operations.

Generation of an optical vortex with a topological charge of l=4 by use of double-pass configuration with an axially-symmetric polarization element

Paper 7950-15 of Conference 7950
Date: Wednesday, 26 January 2011
Time: 4:40 PM – 5:00 PM

Author(s): Kazuhiko Oka, Moritsugu Sakamoto, Naoshi Murakami, Ryuji Morita, Naoshi Baba, Hokkaido Univ. (Japan)
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White-light vortex has attracted attentions because of potential applications such as the ultrafast spectroscopy and the astronomical coronagraph. We previously developed an achromatic method to generate a white-light vortex with a topological charge of l=2, using an axially-symmetric polarization element. The method has a distinct feature that it is free from the spatial- and topological-charge-dispersions, and thereby is suited for use with the broadband light. In this presentation, we describe a modified method with a double-pass configuration to generate the optical vortex with the charge of l=4. The operation of this method was demonstrated with a preliminary experiment.

Ultrafast nonlinear optical properties and excited state dynamics of phthalocyanine thin films

Paper 7935-44 of Conference 7935
Date: Wednesday, 26 January 2011
Time: 6:00 PM

Author(s): Soma Venugopal Rao, Shuvan Prashant Turaga, P. T. Anusha, Swain Debasis, Surya Prakash Tewari, Univ. of Hyderabad (India)
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Phthalocyanines and their metal derivatives possess interesting nonlinear optical properties and find extensive applications in photonic devices such as optical limiters and all-optical switches. For practical applications these materials need to be doped in a suitable matrix. Herein we present our results on the nonlinear optical properties of alkyl and alkoxy phthalocyanine thin films studied using ~2 picosecond and ~40 femtosecond pulses. The nonlinearities were studied using Z-scan technique and the excited state dynamics using the degenerate four wave mixing and pump-probe techniques. A strong nonlinear absorption was observed with both picosecond and femtosecond pulses.

Ultrafast laser fabrication of 3D photonic structures in rare-earth doped glasses and nonlinear optical materials

Paper 7921-14 of Conference 7921
Date: Thursday, 27 January 2011
Time: 8:20 AM – 8:50 AM

Author(s): Kevin P. Chen, Univ. of Pittsburgh (United States)
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In this paper, we present research results on ultrafast laser fabrication of complex multi-layer optical structures in active glass and nonlinear optical materials. Multi-layer 4×4 lightwave circuits were fabricated in silica glass for inter-chip optical interconnect; ring oscillators were fabricated in Nd:YAG ceramic materials for on-chip waveguide laser; and o-ring resonators were laser written in LiNbO3 nonlinear crystals for all-optical optical switching.

Diode-pumped, cryogenically cooled Yb:CaF2 for high efficient and high power laser

Paper 7912-61 of Conference 7912
Date: Thursday, 27 January 2011
Time: 9:20 AM – 9:40 AM

Author(s): Sandrine Ricaud, Amplitude Systemes (France) and Lab. Charles Fabry (France); Frédéric Druon, Institut d'Optique Graduate School (France); Dimitris N. Papadopoulos, Alain Pellegrina, Ecole Nationale Supérieure de Techniques Avancées (France); Patrick Georges, Institut d'Optique Graduate School (France); Antoine Courjaud, Amplitude Systemes (France); Patrice Camy, Jean-Louis Doualan, Richard Moncorgé, ENSICAEN (France)
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We present a high-power diode-pumped Yb:CaF2 laser operating at cryogenic temperature (77 K). A laser output power of 97 W at 1034 nm was extracted for a pump power of 245 W. The corresponding global extraction efficiency (versus absorbed pump power) is 65%. The laser small signal gain was found equal to 3.1. We also studied the influence of the temperature on the thermal conductivity and the thermo-optic coefficients of Yb:CaF2 crystal (doped and undoped) in order to quantitatively evaluate the interest of cryogenic cooling on the heat extraction, the stress and the thermal lens.

High-energy fibre CPA system based on a single stage rod type fiber amplifier in double pass configuration

Paper 7914-55 of Conference 7914
Date: Thursday, 27 January 2011
Time: 11:00 AM – 11:20 AM

Author(s): Yoann Zaouter, Franck Morin, Clemens Hönninger, Eric Mottay, Amplitude Systemes (France)
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We report the generation of high energy, high temporal quality ultrashort pulses from a compact non-linear FCPA setup. The main amplifier uses a state-of-the-art Yb-doped fiber in a double-pass architecture. Thanks to sufficient pulse stretching and good management of dispersion and non-linearities in the system, 250fs pulses with excellent temporal quality and energies of up to 200ตJ are extracted from the system. The achieved pulse peak power of ~750MW is among the highest ever generated by a fiber CPA while the optical setup only requires one single power amplifier and fits in a 1.2m x 0.45m x 0.12m housing.

High-power dissipative soliton laser using chirally-coupled core fiber

Paper 7914-60 of Conference 7914
Date: Thursday, 27 January 2011
Time: 2:20 PM – 2:40 PM

Author(s): Simon Lefrancois, Frank W. Wise, Cornell Univ. (United States); Thomas S. Sosnowski, Arbor Photonics, Inc. (United States); Almantas Galvanauskas, Univ. of Michigan (United States); Chi-Hung Liu, Arbor Photonics, Inc. (United States)
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We report an ultrafast modelocked laser based on large mode-area Chirally-Coupled Core fiber and dissipative soliton pulse shaping. An all-normal dispersion cavity delivers chirped pulse energies above 40 nJ that dechirp below 200 fs, with average powers above 2 W. Peak power is measured in excess of 125 kW. Numerical simulations confirm dissipative soliton pulse shaping. Using a shorter cavity, pulses as short as 105 fs are obtained. This demonstrates that Chirally-Coupled Core fiber delivers sufficiently single-mode performance for systems as sensitive as mode-locked oscillators, while enabling fused fiber component integration.

Developing endoscopic ultrafast laser microsurgery of scarred vocal folds

Paper 7883C-175 of Conference 7883C
Date: Saturday, 22 January 2011
Time: 5:40 PM – 6:00 PM

Author(s): Christopher L. Hoy, The Univ. of Texas at Austin (United States); Murat Yildirim, ; William N. Everett, The Univ. of Texas at Austin (United States); James B. Kobler, Massachusetts General Hospital (United States); Adela Ben-Yakar, The Univ. of Texas at Austin (United States)
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Course: Ultrafast Fiber Lasers

Date: Sunday, 23 January 2011
Time: 8:30 AM – 12:30 PM

Instructor(s): Martin E. Fermann, IMRA America, Inc. (United States)
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Starting from an introduction to fiber lasers, basic properties of fiber amplifiers are reviewed and current state of the art fiber amplifier technology is summarized. The course then describes preferred construction methods for ultrafast fiber lasers and frequency combs and discusses their applications in a variety of optical systems. The course covers mode locked fiber oscillators, phase stabilization techniques, supercontinuum sources, ultrafast fiber amplifiers, frequency converters as well as pulse compressors. Numerous design examples are given, illustrating the recurring physical phenomena governing these systems. The attendee learns about preferred methods for pico- and femtosecond pulse generation in compact fiber systems and basic modeling techniques for pulse evolution, stability, jitter and noise. The course concludes with overviews of applications in materials processing, frequency metrology, spectroscopy and optical sampling.

Ultrafast few-fermion dynamics in single self-assembled InGaAs/GaAs quantum dots and dot molecules

Paper 7937-1 of Conference 7937
Date: Sunday, 23 January 2011
Time: 8:45 AM – 9:10 AM

Author(s): Markus Betz, Technische Univ. Dortmund (Germany)
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We report a comprehensive study of the ultrafast optoelectronic properties of a single self-assembled InGaAs/GaAs quantum dot. While manipulation of the artificial atom relies on two widely and independently tunable picoseconds pulse trains, sensitive readout is achieved via the ~pA photocurrent of the photodiode device. In particular, the absorption changes after occupation of an s-shell exciton reveal a biexciton absorption line as well as previously unobserved p-shell transitions in the presence of s-shell population. In addition, time-resolved data directly maps the picosecond tunneling times of electrons and holes out of the dot. Beyond these incoherent phenomena, we also realize coherent QD manipulations. Those comprise well-known excitonic Rabi-oscillations as well as single-pulse biexciton generation and conditional Rabi-oscillations of the exciton-biexciton transition after deterministic exciton preparation.

Ultrafast modulators based on nonlinear photonic crystal waveguides

Paper 7949-4 of Conference 7949
Date: Sunday, 23 January 2011
Time: 9:05 AM – 9:30 AM

Author(s): Bruce Wessels, Northwestern Univ. (United States)
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Enhancing slow- and fast-light effects in quantum dot semiconductor waveguides through ultrafast dynamics

Paper 7937-8 of Conference 7937
Date: Sunday, 23 January 2011
Time: 12:00 PM – 12:25 PM

Author(s): Yaohui Chen, Jesper Moerk, Technical Univ. of Denmark (Denmark)
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In this paper we review our theoretical work on slow and fast light effects in QD SOAs, in particular we investigate the carrier dynamical contributions to the dynamic gain grating and cross gain modulation induced by unique ultrafast inter-subband carrier dynamics between discrete QD bound states. Our calculations predict that by increasing the injection current density, additional ultra-fast coherent gain contributions around 100GHz arise in contrast to the slow sub-gigahertz CDP effects. For potential applications in microwave photonics, especially targeting the millimeter wave range, we propose that quantum dot devices might be used to realize an optically fed microwave phase shifter in the frequency range of 100GHz.

Compact ultrafast semiconductor disk laser for nonlinear imaging in living organisms

Paper 7903-99 of Conference 7903
Date: Sunday, 23 January 2011
Time: 5:30 PM

Author(s): Rodrigo A. Aviles-Espinosa, ICFO - Instituto de Ciencias Fotónicas (Spain); Giorgos Filippidis, Foundation for Research and Technology-Hellas (Greece); Craig Hamilton, Solus Technologies Ltd. (United Kingdom); Graeme Malcolm, M Squared Lasers Ltd. (United Kingdom); Thomas Südmeyer, Yohan Barbarin, Ursula Keller, ETH Zurich (Switzerland); David Artigas-García, Univ. Politècnica de Catalunya (Spain); Pablo Loza-Alvarez, ICFO - Instituto de Ciencias Fotónicas (Spain)
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Expensive, bulky and complex Ti:sapphire-based ultrafast laser systems have prevented the wide-spread introduction of nonlinear microscopy in biomedical applications. We present the use of a compact semiconductor disk laser (140x240x70 mm) passively modelocked with a quantum-dot SESAM to produce nonlinear images of living C. elegans. The laser delivers 1.5 ps pulses at 500 MHz having an average output power of 287 mW (peak power of 0.5 kW). Its center wavelength located at 965 nm is ideally suited for two-photon excitation of the widely used GFP marker. This non-expensive, turn-key compact laser is ideal for portable nonlinear biomedical imaging devices.

Ultrafast laser assisted micro-injection enables distinct spatial localization pattern in cells and retina

Paper 7897-5 of Conference 7897
Date: Monday, 24 January 2011
Time: 9:30 AM – 9:50 AM

Author(s): Ling Gu, Shivaranjani Shivalingaiah, Samarendra K. Mohanty, The Univ. of Texas at Arlington (United States)
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We report distinct spatial localization of impermeable substances into cells and goldfish retina explants subsequent to injection using ultrafast laser micro-beam. Introduction of Propidium Iodide (PI) dye into the cell through localized pore formation was confirmed by distinct fluorescence response at the site of pore formation on the membrane and its spatiotemporal diffusion pattern through the nucleus. Indirect optoporation by bubble formation, external to cell, led to a similar pattern. Using optimized laser intensity, exposure and spatial irradiation pattern, desired spatial transfection patterns in goldfish retina explants were achieved. We will discuss our initiative and encouraging results in this direction.

Ultrafast gain switching of quantum cascade lasers

Paper 7937-24 of Conference 7937
Date: Monday, 24 January 2011
Time: 10:35 AM – 11:00 AM

Author(s): Sukhdeep S. Dhillon, Nathan Jukam, Dimitri Oustinov, Rakchanok Rungsawang, Julien Madeo, Ecole Normale Supérieure (France); Stefano Barbieri, Christophe Manquest, Carlo Sirtori, Univ. Paris 7-Denis Diderot (France); Suraj P. Khanna, Edmund H. Linfield, Giles Davies, Univ. of Leeds (United Kingdom); Jerome Tignon, Ecole Normale Supérieure (France)
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Terahertz (THz) time domain spectroscopy is now a widely used technique where it is essential to know both the amplitude and phase of a THz wave. Nonetheless, THz amplifiers, capable of increasing the THz wave field, are presently lacking. In this context THz quantum cascade lasers (QCL) are very promising devices for amplification. Gain clamping in these devices, however, limits the attainable amplification. Here we circumvent gain clamping by coupling a THz QCL and an integrated Auston-switch to perform ultrafast gain switching. The resulting non-equilibrium gain is not clamped above laser threshold and large amplification of input terahertz pulses is demonstrated.

Coherent control of ultrafast photocurrents in GaAs

Paper 7937-30 of Conference 7937
Date: Monday, 24 January 2011
Time: 1:55 PM – 2:20 PM

Author(s): Sangam Chatterjee, Kapil K. Kohli, Jan Mertens, Philipps-Univ. Marburg (Germany); Mark Bieler, Physikalisch-Technische Bundesanstalt (Germany)
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The relationship between the electrical field of an optical pulse and its encompassing pulse envelope is characterized by the carrier-envelope phase (CEP). We show, that by using a phase stable pulse pair generated in a pulse shaper we can use the relative CEP between the two pulses as a new degree of freedom in coherent control experiments even for pulses that are not in the single-cycle regime. We demonstrate how to use the CEP to coherently control the shift current generation process in bulk GaAs, by measuring the emitted THz radiation in a standard THz emission setup. A straightforward theoretical model corroborates our experiment.

Ultrafast coherent optoelectronics of semiconductor-metal hybrid structures

Paper 7937-31 of Conference 7937
Date: Monday, 24 January 2011
Time: 2:20 PM – 2:45 PM

Author(s): Claudia Ruppert, Technische Univ. München (Germany); Markus Betz, Technische Univ. Dortmund (Germany)
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We report on two sets of experiments whereby femtosecond near-infrared pulses are utilized to demonstrate optoelectronic functionalities of nanodevices. First, coherent control techniques are used to generate ballistic photocurrents in nanowires. In particular, illuminating a GaAs nanowire with a phase stable superposition of 1550 nm femtosecond pulses and their second harmonic, ~ตA ballistic electrical currents are generated without an external bias. The second part is related to the excitation of surface plasmon polaritons (SPPs) in plain and unstructured gold films. In contrast to established SPP launchers based on permanent gratings, we utilize LiNbO_3 surface acoustic waves underneath a metal thin film to create dynamic gratings with variable period and amplitude as well as nanosecond switching times.

Ultrafast hot carrier dynamics in InN epitaxial films

Paper 7937-35 of Conference 7937
Date: Monday, 24 January 2011
Time: 4:30 PM – 4:55 PM

Author(s): Tsongru Tsai, Chih-Fu Chang, Chih-Wei Kuo, Cheng-Yu Chang, National Taiwan Ocean Univ. (Taiwan); S. Gwo, National Tsing Hua Univ. (Taiwan)
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Ultrafast hot carrier dynamics in Indium nitride (InN) epitaxial films were investigated by femtosecond time-resolved pump-probe reflectivity measurements. Carrier density and carrier energy dependence of the hot carrier dynamics in InN were studied by varying the pump laser power and wavelength, respectively. Experimental results show that the hot carrier relaxation can be fitted by a biexponential relaxation process. The fast relaxation rate increases with increasing carrier density (N), which is measured as N0.5. The fast relaxation rate also increases with increasing carrier energy (E), which is measured as E0.53. These observations reveal that the electron-electron scattering plays an important role in hot carrier relaxation. In addition, the slow relaxation is dominated by Auger scattering and the slow relaxation rate is independent of the carrier energy. The defect-related trapping time in InN was estimated to be ~515 ps.

Quasi-ballistic thermal transport from nanoscale interfaces observed using ultrafast coherent soft x-ray beams

Paper 7937-41 of Conference 7937
Date: Tuesday, 25 January 2011
Time: 11:35 AM – 12:00 PM

Author(s): Mark E. Siemens, Univ. of Denver (United States); Qing Li, Ronggui Yang, Univ. of Colorado at Boulder (United States); Keith A. Nelson, Massachusetts Institute of Technology (United States); Erik H. Anderson, Lawrence Berkeley National Lab. (United States); Margaret M. Murnane, Henry C. Kapteyn, Univ. of Colorado at Boulder (United States)
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Heat dissipation from a nanoscale hot-spot is expected to be non-diffusive for hot-spots smaller than the phonon mean free path of the substrate. Our technique of observing diffraction of coherent soft x-ray pulses allows for very high resolution (~pm) of surface distortion, as well as femtosecond time resolution of dynamics. We successfully model our experimental results with a diffusive transport model, modified to include an additional boundary resistance. These results confirm the importance of considering ballistic transport away from a nanoscale heat source, and identify a means of correctly accounting for this ballistic transport.

Course: Introduction to Ultrafast Technology

Date: Tuesday, 25 January 2011
Time: 1:30 PM – 5:30 PM

Instructor(s): Rick P. Trebino, Georgia Institute of Technology (United States)
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Ultrafast Optics-the science, technology, and applications of ultrashort laser pulses-is one of the most exciting and dynamic fields of science. While ultrashort laser pulses seem quite exotic (they're the shortest events ever created!), their applications are many, ranging from the study of ultrafast fundamental events to telecommunications to micro-machining to biomedical imaging, to name a few. Interestingly, these lasers are easy to understand, and they are readily available. But their use requires some sophistication. This course is a basic introduction to the nature of these lasers, their use, and some of their applications.

Real time ultrafast optical interferometry of NEMS operating in fluidic environment

Paper 7929-29 of Conference 7929
Date: Tuesday, 25 January 2011
Time: 4:50 PM – 5:10 PM

Author(s): Oleksiy Svitelskiy, The Univ. of North Carolina at Charlotte (United States); Vince Sauer, National Institute for Nanotechnology (Canada); Ning Liu, Univ. of Alberta (Canada); Kar-Mun Cheng, Eric Finley, National Institute for Nanotechnology (Canada); Mark R. Freeman, National Institute for Nanotechnology (Canada) and Univ. of Alberta (Canada); Wayne K. Hiebert, National Institute for Nanotechnology (Canada)
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Interactions of NEMS with fluids are of interest both in determining the NEMS performance outside of vacuum, and in elucidation of fluid dynamics at these small scales. We present a comprehensive study of nanomechanical damping in three gases (He, N2, CO2), and liquid CO2. Resonant dynamics in multiple devices of varying size and frequency (10-400 MHz) is measured over 10 decades of pressure (1 mPa-20 MPa). We find a fluid relaxation time model to be valid throughout, but not beyond, the non-Newtonian regime (up to several atmospheres), and classical vibrating spheres model to be valid in the viscous limit.

Scaling high-power ultrafast VECSELs into the femtosecond regime

Paper 7919-25 of Conference 7919
Date: Tuesday, 25 January 2011
Time: 9:30 PM – 9:45 PM

Author(s): Oliver D. Sieber, Martin Hoffmann, Valentin J. Wittwer, Wolfgang P. Pallmann, Yohan Barbarin, Matthias C. Golling, Thomas Südmeyer, Ursula Keller, ETH Zurich (Switzerland)
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The combination of high output power and femtosecond pulses from VECSELs and MIXSELs would be very attractive for many applications. To explore the limitations, a quantitative understanding of the pulse formation processes is required. Our numerical simulations showed a good qualitative agreement with experimental results in the picosecond regime. By minimizing intracavity group delay dispersion (GDD) and improving gain bandwidth and SESAM parameters, our model predicts pulses as short as 750 fs. As a first step we minimized GDD with a top coating which provides values between ฑ10 fs2 over a range of 30 nm around the design wavelength.

Ultrafast switching of light by absorption saturation in vacuum ultraviolet region

Paper 7937-55 of Conference 7937
Date: Wednesday, 26 January 2011
Time: 9:05 AM – 9:30 AM

Author(s): Hitoki Yoneda, The Univ. of Electro-Communications (Japan); Yuichi Inubushi, Osaka Univ. (Japan); Fumiya Sato, The Univ. of Electro-Communications (Japan); Shunsuke Morimoto, Taisuke Kumagaya, Osaka Univ. (Japan); Mitsuru Nagasono, Atsushi Higashiya, Makina Yabashi, Tetsuya Ishikawa, Haruhiko Ohashi, Hiroaki Kimura, Tadashi Togashi, RIKEN (Japan); Hikaru Kitamura, Kyoto Univ. (Japan); Ryosuke Kodama, Osaka Univ. (Japan)
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Recent sub-picosecond pulses of extreme ultra-violet light from free electron lasers open new possibilities for nonlinear optics in higher photon energy science. In this work we report observation of nonlinear phenomena in the 50-60 nm EUV wavelength region. We have observed (1) high contrast saturable absorption in Sn1, and (2) multi-step photon absorption in Ti. Based on these two typical experimental results, we can start to develop new nonlinear photonic devices such as auto-correlator and pulse slicer for the EUV region

Microscopic theory of ultrafast processes in carbon nanomaterials

Paper 7937-62 of Conference 7937
Date: Wednesday, 26 January 2011
Time: 1:50 PM – 2:15 PM

Author(s): Ermin Malic, Torben Winzer, Andreas Knorr, Technische Univ. Berlin (Germany)
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We have performed microscopic investigations of the phonon- and Coulomb-induced relaxation dynamics of photo-excited carriers in graphene and single-walled carbon nanotubes. Based on microscopic calculation within the density matrix formalism we show that the electron-electron scattering thermalizes the electronic system within first hundred femtoseconds followed by a fast energy dissipation arising from the electron-phonon coupling. Furthermore, we show that due to its zero-bandgap Auger-type processes play an unusually significant role for understanding the carrier dynamics in graphene. In particular, we observe a considerable carrier multiplication due to the efficient impact ionization.

Ultrafast exciton and charge transfer in small aggregates of carbon nanotubes

Paper 7937-65 of Conference 7937
Date: Wednesday, 26 January 2011
Time: 3:05 PM – 3:30 PM

Author(s): Larry Lüer, Instituto Madrileño de Estudios Avanzados (Spain); Jared Crochet, Los Alamos National Lab. (United States); Tobias Hertel, Univ. of Würzburg (Germany); Sajjad Hoseinkhani, Italian Institute of Technology (Italy); Giulio Cerullo, Politecnico di Milano (Italy); Guglielmo Lanzani, Italian Institute of Technology (Italy)
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We studied excitation energy transfer in small hexagonal aggregates of carbon nanotubes by femtosecond spectroscopy with down to 7 fs pulse duration. After resonant excitation of the first excitonic transition in (6,5) tubes, we found that excitons are transferred towards (7,5) tubes within less than 10 fs. After pumping at high photon energies, favoring the formation of free carriers, we found clear spectroscopic signatures allowing us to trace ultrafast charge transfer, trapping and recombination.

Graphene mode locked ultrafast fiber lasers

Paper 7914-53 of Conference 7914
Date: Thursday, 27 January 2011
Time: 9:30 AM – 10:00 AM

Author(s): Dingyuan Tang, Han Zhang, Nanyang Technological Univ. (Singapore); Qiaoliang Bao, Kian Ping Loh, National Univ. of Singapore (Singapore)
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We show experimentally that graphene possesses ultrafast saturable absorption, which can be used for mode locking of fiber lasers. Either the pristine graphene or graphene-polymer nanocomposite was used for mode locking erbium-doped fiber lasers. It was found that stable mode locked pulses could always be obtained, and the mode locked pulses could have much larger energy than those obtained with SESAM or CNT mode locking techniques. A unique property of graphene saturable absorption is its wavelength independence. Taking advantage of the property we have achieved wide range (~ 30nm) wavelength tunable soliton operation in erbium-doped fiber lasers. In addition, a graphene mode locked Yb-doped fiber laser operating at 1.06 micrometer was also demonstrated.

Holographic spatiotemporal lens (HSTL)

Paper 7925-7 of Conference 7925
Date: Sunday, 23 January 2011
Time: 11:40 AM – 12:00 PM

Author(s): Kouhei Kimura, Satoshi Hasegawa, Yoshio Hayasaki, Utsunomiya Univ. (Japan)
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We propose a holographic spatiotemporal lens (HSTL) to improve spatial resolution of two-photon excitation spot as a new focusing technique of femtosecond laser pulse. Femtosecond laser pulses dispersed by a diffraction grating or a prism-pair are irradiated to a chirped diffractive lens (CSTL) displayed on a spatial light modulator (SLM). The CDL has a spatially chirp of focal length for a design for its corresponding wavelength. The shortest pulse was experimentally obtained only at the focal plane. The pulse duration was also supported with a computer simulation. Furthermore, we demonstrated parallel spatiotemporal focusing using a multiplexed HSTL.

Experimental investigation of wavelength dependence of penetration depth and imaging contrast for ultra-high-resolution optical coherence tomography

Paper 7889-92 of Conference 7889
Date: Monday, 24 January 2011
Time: 5:30 PM

Author(s): Shutaro Ishida, Norihiko Nishizawa, Nagoya Univ. (Japan); Kazuyoshi Itoh, Osaka Univ. (Japan)
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We investigated the wavelength dependence of penetration depth and imaging contrast for biological samples with ultrahigh resolution optical coherence tomography at 0.8 um, 1.3 um, and 1.7 um wavelength region. In each system, we set the adequate optical components using the same composition system. We achieved 3.6 um, 7.9 um, and 6.0 um ultrahigh longitudinal resolutions in air and have more than 90 dB sensitivity. The 1.7 um OCT image had deeper penetration depth and high imaging contrast from other wavelength systems for biological samples. It is expected to be useful for ultrahigh-resolution OCT imaging applications.

Power scaling of the MIXSEL: an integrated picosecond semiconductor laser with >6 W average power

Paper 7919-27 of Conference 7919
Date: Tuesday, 25 January 2011
Time: 10:30 AM – 11:00 AM

Author(s): Thomas Südmeyer, ETH Zurich (Switzerland)
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Semiconductor lasers have to potential to drastically reduce complexity and cost of high power ultrafast lasers. Optically-pumped VECSELs achieved >20 W cw-power in fundamental transverse mode. Passive modelocking with a SESAM enabled 2.1-W average power, sub-100 fs duration, and 50-GHz repetition rate. In 2007, the integration of both elements was demonstrated, the MIXSEL (modelocked integrated external-cavity surface-emitting laser). Here we present a novel MIXSEL design based on a low-saturation fluence quantum dot (QD) absorber layer in an anti-resonant structure. Improved thermal management with a CVD-diamond enabled a >30-fold power increase to 6.4 W, higher than any other ultrafast semiconductor laser.

The effect of ambient conditions on thin wafers processed with fs-laser machining

Paper 7920-36 of Conference 7920
Date: Tuesday, 25 January 2011
Time: 10:50 AM – 11:20 AM

Author(s): Sae Chae Jeoung, Korea Research Institute of Standards and Science (Korea, Republic of)
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Micromachining based on laser has become important tools in the fields of mass production for modern ?-devices including multi-layered microelectronics, LED, solar voltaic cells, displays, multilayered PCB and so on. While conventional mechanical processes have come to their limitations in the course of size miniaturization, ultrafast laser techniques have been known to have a potential application in high precision processing because of their minimized heat affected zone. The other potential application of fs-laser ?-processing is to modify the surface to form functional micro- and nanostructures. We will present the effects of ambient processing conditions on the surface topological changes as well as the mechanical properties of processed materials. For example, we observe that ambient gases and laser fluence used in processing play an important role in encapsulation of Ge nanostructures with oxidized layer as well as their size distribution. Further, the substrate temperature of silicon wafers also affects the dependence of surface roughness on the laser fluence. This observation can be understood in terms of the changes in ablation mechanism underlying fs-laser material ablation process between optical penetration and thermal diffusion processes. We also propose an empirical relation between maximum yield stress and cumulative temperature increment of dielectric materials based on the measurement of the stress of small die formed with varying the repetition rate of fs-laser pulse and the ambient gas. The current work should be helpful to understand the effect of ambient conditions on fs-laser-material interaction for practical usage.

The effect of ambient conditions on thin wafers processed with fs-laser machining

Paper 7925-36 of Conference 7925
Date: Tuesday, 25 January 2011
Time: 10:50 AM – 11:20 AM

Author(s): Sae Chae Jeoung, Korea Research Institute of Standards and Science (Korea, Republic of)
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Micromachining based on laser has become important tools in the fields of mass production for modern ?-devices including multi-layered microelectronics, LED, solar voltaic cells, displays, multilayered PCB and so on. While conventional mechanical processes have come to their limitations in the course of size miniaturization, ultrafast laser techniques have been known to have a potential application in high precision processing because of their minimized heat affected zone. The other potential application of fs-laser ?-processing is to modify the surface to form functional micro- and nanostructures. We will present the effects of ambient processing conditions on the surface topological changes as well as the mechanical properties of processed materials. For example, we observe that ambient gases and laser fluence used in processing play an important role in encapsulation of Ge nanostructures with oxidized layer as well as their size distribution. Further, the substrate temperature of silicon wafers also affects the dependence of surface roughness on the laser fluence. This observation can be understood in terms of the changes in ablation mechanism underlying fs-laser material ablation process between optical penetration and thermal diffusion processes. We also propose an empirical relation between maximum yield stress and cumulative temperature increment of dielectric materials based on the measurement of the stress of small die formed with varying the repetition rate of fs-laser pulse and the ambient gas. The current work should be helpful to understand the effect of ambient conditions on fs-laser-material interaction for practical usage.

A femtosecond laser inscribed biochip for stem cell therapeutic applications

Paper 7929-22 of Conference 7929
Date: Tuesday, 25 January 2011
Time: 12:10 PM – 12:30 PM

Author(s): Debaditya Choudhury, William T. Ramsay, Nicholas D. Psaila, Graeme Brown, Stephen Beecher, Lynn Paterson, Ajoy K. Kar, Robert Kiss, Nicholas A. Willoughby, Heriot-Watt Univ. (United Kingdom); Steve Pells, The Univ. of Edinburgh (United Kingdom)
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For over 30 years, the extraordinary regenerative and replenishing properties of stem cells have been utilised in cancer research. Although promising advances have been made in the field, a complete clinical outcome remains elusive. A fundamental impediment involves therapeutic use of human embryonic stem cells, which is accompanied by a significant risk of cancer progression if the therapeutic implant is not entirely free of stem cells. We report on the realisation of a femtosecond laser inscribed biochip in fused silica that segregates human embryonic stem cells from their differentiated progeny based on the dissimilarity in cytoskeletal elasticity of the cells.

Nanostructure formation on silicon surfaces by high repetition-rate sub-15fs near-infrared laser pulses

Paper 7920-26 of Conference 7920
Date: Tuesday, 25 January 2011
Time: 4:40 PM – 5:00 PM

Author(s): Martin H. Straub, Karsten König, Univ. des Saarlandes (Germany)
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On low-indexed crystalline silicon surfaces characteristic micro- and nanostructures are formed using high repetition-rate sub-15 fs Ti:Sapphire laser pulses. Sub-nJ pulse energies efficiently induce profound structural and compositional changes in the high-numerical aperture focus of our laser scanning microscope. For example, a Si(100) surface exposed to laser light in water revealed periodic changes in morphology involving oxide particle formation and sub-10 nm hole arrangements, whereas a similar experiment in oil resulted in nano-scale deposition of carbon compounds. We present novel investigations as well as analysis and discussion of phenomena and compare results with observations made using longer pulse widths.

Nanostructure formation on silicon surfaces by high repetition-rate sub-15fs near-infrared laser pulses

Paper 7925-26 of Conference 7925
Date: Tuesday, 25 January 2011
Time: 4:40 PM – 5:00 PM

Author(s): Martin H. Straub, Karsten König, Univ. des Saarlandes (Germany)
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On low-indexed crystalline silicon surfaces characteristic micro- and nanostructures are formed using high repetition-rate sub-15 fs Ti:Sapphire laser pulses. Sub-nJ pulse energies efficiently induce profound structural and compositional changes in the high-numerical aperture focus of our laser scanning microscope. For example, a Si(100) surface exposed to laser light in water revealed periodic changes in morphology involving oxide particle formation and sub-10 nm hole arrangements, whereas a similar experiment in oil resulted in nano-scale deposition of carbon compounds. We present novel investigations as well as analysis and discussion of phenomena and compare results with observations made using longer pulse widths.

Efficient spherical wavefront correction near the focus of the petawatt-level femtosecond CPA laser system

Paper 7916-36 of Conference 7916
Date: Tuesday, 25 January 2011
Time: 6:00 PM

Author(s): Zhijun Ren, Xiaoyan Liang, Lianghong Yu, Xiaoming Lu, Ruxin Li, Zhizhan Xu, Shanghai Institute of Optics and Fine Mechanics (China)
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By directly measuring the spherical wavefront near the focus, we demonstrated a approach to efficiently correct convergent spherical wavefront by installing a common small aperture deformable mirror (DM) in the middle of 0.89PW/29.0fs Ti:sapphire CPA laser chain. It is, to our knowledge, the first time attain the near perfect correction result in ultra-intensity laser system by correcting convergent spherical wavefront using a small aperture DM in adaptive optical loop. Finally the maximum peak intensity of 2.36×10^21 W/cm2 was obtained with an f/4 off-axis parabola at the output power of 0.89 PW.

Integrated lab-on-a-chip: a combined sample preparation and PCR system as an ultrafast analytical tool for pathogen detection

Paper 7929-1 of Conference 7929
Date: Sunday, 23 January 2011
Time: 2:30 PM – 3:00 PM

Author(s): Holger Becker, Nadine Hlawatsch, Richard Klemm, Claudia Gärtner, microfluidic ChipShop GmbH (Germany)
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The overall aim is the realization of a reliable, ultrafast, and portable system for the identification of pathogens and other B-agents at the point of interest. PCR is the method to be used for the unambiguous identification of e.g. bacteria, and viruses. Miniaturization is the way to include the overall analysis process, from sample preparation to detection, on a microtiterplate-sized consumable device and to allow to carry out the analysis without the need for an equipped biological laboratory.

Integrated lab-on-a-chip: a combined sample preparation and PCR system as an ultrafast analytical tool for pathogen detection

Paper 7888-1 of Conference 7888
Date: Sunday, 23 January 2011
Time: 2:30 PM – 3:00 PM

Author(s): Holger Becker, Nadine Hlawatsch, Richard Klemm, Claudia Gärtner, microfluidic ChipShop GmbH (Germany)
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The overall aim is the realization of a reliable, ultrafast, and portable system for the identification of pathogens and other B-agents at the point of interest. PCR is the method to be used for the unambiguous identification of e.g. bacteria, and viruses. Miniaturization is the way to include the overall analysis process, from sample preparation to detection, on a microtiterplate-sized consumable device and to allow to carry out the analysis without the need for an equipped biological laboratory.

Autofluorescence suppression in fluorescence tomography of quantum dots using time-gated detection and ultrafast pulsed laser

Paper 7896-68 of Conference 7896
Date: Wednesday, 26 January 2011
Time: 11:20 AM – 11:40 AM

Author(s): Xiaofeng Zhang, Cristian Badea, G. Allan Johnson, Duke Univ. (United States)
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Quantum dots (QDs) are being used widely in fluorescence tomography because they are highly quantum-efficient, photostable, engineerable, and conjugatable. Despite these advantages of QDs for in vivo animal imaging, autofluorescence is still one of the most fundamental limitations in optical data acquisition. We explore the fact that the QDs have very long fluorescent life-time compared to proteins, to suppress background noise due to autofluorescence. Fluorescent emission from the QDs was excited using an ultrafast pulsed laser, and was detected using a time-gated imaging intensifier. Using an imaging phantom, this method showed significant improvement over non-time-gated acquisition.

High aspect ratio taper-free micro and nano-channel fabrication in glass with ultrafast nondiffracting Bessel beams

Paper 7921-18 of Conference 7921
Date: Thursday, 27 January 2011
Time: 10:30 AM – 11:00 AM

Author(s): Manoj K. Bhuyan, Francois Courvoisier, Maxime Jacquot, Pierre-Ambroise Lacourt, Roland Salut, Luca Furfaro, John M. Dudley, Univ. de Franche-Comté (France)
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We review our recent results on femtosecond laser processing of micro and nano-channels in glass with nondiffracting Bessel beams. We show that these beams allow for an in-depth control of energy deposition, contrary to Gaussian beams. In the multishot regime, taper-free microchannels with aspect ratio up to 40 can be processed without beam translation. In the single shot regime, we demonstrate the processing of terminated nanochannels and through-channels with aspect ratio up to 100 with diameters in the range 200-800 nm. We interpret our results in terms of stationarity of the nonlinear Bessel beam propagation at ablation-level intensities.

Course: Principles and Applications of Optical Coherence Tomography

Date: Sunday, 23 January 2011
Time: 1:30 PM – 5:30 PM

Instructor(s): James G. Fujimoto, Massachusetts Institute of Technology (United States)
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Optical coherence tomography (OCT) is a new imaging modality, which is the optical analog of ultrasound. OCT can perform high resolution cross sectional imaging of the internal structure of biological tissues and materials. OCT is promising for biomedical imaging because it functions as a type of optical biopsy, enabling tissue pathology to be imaged in suit and in real time. This technology also has numerous applications in other fields ranging from nondestructive evaluation of materials to optical data storage. This course describes OCT and the integrated disciplines including fiber optics, interferometry, high-speed optical detection, biomedical imaging, in vitro and in vivo studies, and clinical medicine

Parallel fluorescence photon timing module with monolithic SPAD array detector

Paper 7905-2 of Conference 7905
Date: Saturday, 22 January 2011
Time: 9:00 AM – 9:20 AM

Author(s): Ivan Rech, Angelo Gulinatti, Corrado Cammi, Francesco Panzeri, Massimo Ghioni, Politecnico di Milano (Italy)
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Over the past few years there has been a growing interest in monolithic arrays of single photon avalanche diodes (SPAD) for time resolved detection of faint ultrafast optical signals. SPADs implemented in CMOS-compatible planar technologies offer the typical advantages of microelectronic devices (small size, ruggedness, low voltage, low power, etc.). Furthermore, they have inherently higher photon detection efficiency than PMTs and are able to provide, beside sensitivities down to single-photons, very high acquisition speeds. A compact module based on a 8x1 high performance time resolved SPAD array is here presented.

Integrated Terahertz pulse generation and amplification in quantum cascade lasers

Paper 7945-11 of Conference 7945
Date: Sunday, 23 January 2011
Time: 11:20 AM – 11:40 AM

Author(s): Sukhdeep S. Dhillon, Simon Sawallich, Nathan Jukam, Dimitri Oustinov, Julien Madeo, Rakchanok Rungsawang, Ecole Normale Supérieure (France); Stefano Barbieri, Pascal G. Filloux, Carlo Sirtori, Univ. Paris 7-Denis Diderot (France); Xavier Marcadet, Alcatel-Thales III-V Lab. (France); Jerome Tignon, Ecole Normale Supérieure (France)
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We demonstrate an integrated approach to generate and amplify Terahertz (THz) pulses within a quantum cascade laser (QCL). Using an ultrafast interband excitation of a THz QCL, THz pulses are generated via charge carrier acceleration within the QCL miniband. The generated pulses are subsequently amplified at the QCL gain as they propagate through the laser cavity. As well as integrating the generation and amplification of THz pulses, this technique can potentially permit efficient THz pulse injection into sub-wavelength double metal resonators.

Advances in lasers for multiphoton biological imaging

Paper 7903-20 of Conference 7903
Date: Sunday, 23 January 2011
Time: 4:05 PM – 4:20 PM

Author(s): David P. Armstrong, Coherent, Inc. (United States)
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Key to future advances in multiphoton biological imaging is the ability to work with a wider range of fluorophores, to image deeper into samples and to minimize sample damage. In terms of laser characteristics, these requirements translate into wider tuning range and sufficient excitation (average and peak power). This paper explores the advances in tunable ultrafast sources, both laser and OPO, to meet these goals and thus power the next generation of MPE instrumentation.

In-depth fiber optic two-photon polymerization and its applications in micromanipulation

Paper 7927-44 of Conference 7927
Date: Tuesday, 25 January 2011
Time: 6:00 PM

Author(s): Yogeshwar N. Mishra, Ninad D. Ingle, Samarendra K. Mohanty, The Univ. of Texas at Arlington (United States)
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Two photon polymerization (TPP) has enabled three-dimensional microfabrication with sub-diffraction limited spatial resolution. However, the depth at which TPP could be achieved has been limited due to the high numerical aperture microscope objective, used to focus the ultrafast laser beam. With the use of an axicon tip (fabricated by chemical etching method), in-depth FTP structures were formed on flat as well as curved surfaces. We will present microfabrication using fiber-optic TPP and micromanipulation of microscopic objects using such microfabricated structures.

Enhanced supercontinuum generation by minute continuous wave seed

Paper 7917-32 of Conference 7917
Date: Wednesday, 26 January 2011
Time: 2:10 PM – 2:30 PM

Author(s): Ka Yi K. Cheung, Yue Zhou, Kin-Yip K. Wong, Kevin K. Tsia, The Univ. of Hong Kong (Hong Kong, China)
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We demonstrate an enhanced supercontinuum (SC) generation by employing an extremely weak continuous wave (CW) seed signal (~1000 times smaller than the pump). The CW-seeded SC shows considerable spectral broadening (>100 nm wider), enhancement in output intensity (>20dB), and improvement in SC coherence. The fact that the present CW seeding scheme only requires the seed-wavelength tuning for optimization renders itself a convenient and practical approach to actively control an enhanced and stable SC for a myriad of applications, especially in which real-time, ultrafast and single-shot spectroscopic measurements are essential.

Spin induced gigahertz polarization oscillations in vertical-cavity surface-emitting laser devices

Paper 7952-10 of Conference 7952
Date: Wednesday, 26 January 2011
Time: 2:10 PM – 2:30 PM

Author(s): Mingyuan Li, Jaehme Hendrik, Henning Soldat, Nils C. Gerhardt, Martin R. Hofmann, Ruhr-Univ. Bochum (Germany); Thorsten Ackemann, Univ. of Strathclyde (United Kingdom)
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Spin-polarized lasers are attractive for applications in communication technology because their output polarization can potentially be modulated extremely fast. We investigate the temporal circular polarization dynamics of electrically pumped vertical-cavity surface-emitting lasers after additional pulsed spin injection at room temperature. The experimental results demonstrate ultrafast circular polarization oscillations due to pulsed spin injection in the vicinity of a polarization switching point with a frequency of 11.6 GHz and a duration longer than 5 ns. Via theoretical calculations based on rate equation models we analyze and explain the coupling mechanism of these oscillations.

Thermally managed Z-scan measurements of titanium dioxide thin films

Paper 7917-54 of Conference 7917
Date: Thursday, 27 January 2011
Time: 2:35 PM – 2:55 PM

Author(s): Christopher C. Evans, Jonathan D. B. Bradley, Francois Parsy, Katherine C. Phillips, Ruwan Senaratne, Erwin A. Marti-Panameño, Eric D. Mazur, Harvard Univ. (United States)
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We will present measurements of the complex nonlinear response of sputtered amorphous and polycrystalline titanium dioxide (TiO2) thin films using the thermally managed z-scan technique. Using a Ti:Sapphire laser with 100-fs pulses at 800 nm, we observe ultrafast electronic effects near TiO2's half band-gap. We explore the relation between material processing parameters and observed nonlinearity. In addition, we will discuss the consequences for applications such as all-optical switching.

Course: Nanoplasmonics

Date: Wednesday, 26 January 2011
Time: 8:30 AM – 5:30 PM

Instructor(s): Mark I. Stockman, Georgia State Univ. (United States)
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Nanooptics deals with optical phenomena and spectroscopy on the nanoscale, i.e., in the regions of space whose size is much smaller than the light wavelength. While electromagnetic waves cannot be localized in the regions with sizes significantly less than half wavelength, nanooptics is based on electric fields oscillating at optical frequency. From the positions of the interaction with matter and spectroscopy, such local optical fields mostly produce the same type of responses as electromagnetic waves. Elementary excitations that are carriers of energy and coherence in nanooptics are surface plasmons (SPs). These local fields cause a wealth of gigantically enhanced optical phenomena of which the surface enhanced Raman scattering (SERS) is the most studied and widely known. This one-day course will encompass the fundamental properties and applications of the surface plasmonics at the nanoscale. It will include coherent effects associated with phase memory of the SPs, in particular, coherent control of nanooptical phenomena. Nonlinear processes such as generation of harmonics and two-photon excitation by nanoscale fields will also be covered. Ultrafast (femtosecond and attosecond) phenomena are within the scope of this course. We will also include quantum phenomena associated with properties of surface plasmons as quantum quasiparticles such as quantum generation and fluctuations. Along with fundamental properties of SPs, we will consider many applications of nanoplasmonics, in particular, detection of ultrasmall amounts of chemical and biological compounds, scanning near-field optical microscopes or SNOMs, and nanolithography.

High-throughput in-vivo vertebrate imaging and screening (Keynote Presentation)

Paper 7902-9 of Conference 7902
Date: Saturday, 22 January 2011
Time: 1:55 PM – 2:15 PM

Author(s): Mehmet F. Yanik, Carlos Pardo, Tsung-Yao Chang, Bryan Koo, Cody Gilleland, Steven Wasserman V.D.M., Massachusetts Institute of Technology (United States)
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We demonstrate the first high-throughput platform for cellular-resolution in vivo pharmaceutical and genetic screens on vertebrates (Nature Methods, August 2010). The system automatically loads zebrafish from multiwell plates, and positions and orients them for high-speed multifocal confocal imaging and ultrafast laser manipulation of both superficial and deep organs within 19sec without damage. We show screening of retinal axon guidance mutants and neuronal regeneration assays in combination with femtosecond laser microsurgery. Our technology can permit large-scale in vivo drug screens on organ development, neural degeneration/regeneration, stem cell proliferation, cardiovascular, immune, and endocrine systems, pathogenesis, cancer, and toxicity of drugs on vertebrates.

Live atomic force microscopy imaging of laser microbeam-assisted cellular microsurgery

Paper 7902-18 of Conference 7902
Date: Sunday, 23 January 2011
Time: 8:30 AM – 8:50 AM

Author(s): Ninad D. Ingle, Samarendra K. Mohanty, The Univ. of Texas at Arlington (United States)
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Since the invention of lasers, laser microbeam has been employed to cause highly localized damage to cellular and sub-cellular organelles. With the advent of ultrafast lasers, the spatial extent of damage has been reduced to sub-wavelength dimensions, thus enabling precise nano-surgery with the least amount of collateral damage. Simultaneous fluorescence imaging could be realized during laser exposure and AFM imaging. AFM imaging revealed subtle trenches created by defocusing or aberration, which could not be obtained by conventional microscopy. Further, no resealing was observed in dry RBC samples. We will present the dynamics of hole formation and resealing on live RBC membrane.

Microfluidic manipulations with sub-cellular optical resolution

Paper 7943-2 of Conference 7943
Date: Sunday, 23 January 2011
Time: 11:00 AM – 11:30 AM

Author(s): Mehmet F. Yanik, Massachusetts Institute of Technology (United States)
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We present microfluidic and ultrafast optical technologies for studying complex physiological processes in vivo such as neuronal regeneration and degeneration, and stem cell proliferation in both invertebrate and vertebrate animal models. These technologies include microfluidic whole-animal manipulators, as well as integrated chips containing multiple addressable incubation chambers for exposure of individual animals to compounds and for sub-cellular time-lapse imaging of hundreds of animals on single chips. Using femtosecond laser nanosurgery, we performed the first in vivo screen for compounds enhancing neuronal regrowth. We discovered highly potent compounds with a wide variety of cellular targets that enhance neuronal regeneration.

Damping of acoustic vibrations in gold nanoparticles

Paper 7937-16 of Conference 7937
Date: Sunday, 23 January 2011
Time: 4:25 PM – 4:50 PM

Author(s): Matthew A. Pelton, Argonne National Lab. (United States); John Sader, The Univ. of Melbourne (Australia); Mingzhao Liu, Harvard Univ. (United States); Yiliang Wang, Argonne National Lab. (United States); Julien Burgin, Institut de Chimie de la Matière Condensée de Bordeaux (France); Philippe Guyot-Sionnest, The Univ. of Chicago (United States); David Gosztola, Argonne National Lab. (United States)
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We used ultrafast pump-probe laser spectroscopy to measure acoustic vibrations of colloidal gold nanoparticles. Although these vibrations have been studied for several years, decay of the measured signal has previously been dominated by inhomogeneous dephasing due to variations in nanoparticle size. We have overcome this limitation by investigating a highly monodisperse sample of bipyramidal gold nanoparticles. The inferred homogeneous damping is due to the combination of damping intrinsic to the nanoparticles and damping by the surrounding solvent; the fluid damping, in particular, is quantitatively described by a parameter-free analytical model.

Two-photon excitation STED-CW microscopy

Paper 7903-101 of Conference 7903
Date: Sunday, 23 January 2011
Time: 5:30 PM

Author(s): Paolo Bianchini, Silvia Galiani, Alberto Diaspro, Istituto Italiano di Tecnologia (Italy)
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Here, we report sub-diffraction resolution in two-photon excitation (TPE) fluorescence microscopy achieved by merging this technique with continuous-wave (CW) stimulated-emission depletion (STED). We show an easy-to- implement and promising laser combination based on Ti:Sapphire ultrafast laser source for two-photon excitation and a commercial Leica STED-CW microscope for resolution enhancement. Images of fluorescent nanoparticles produce comparative similar resolution to the one photon excitation. Two-photon excitation STED microscopy achieves approximately 3-fold improvement in resolution in the radial direction over conventional 2PELSM. Further improvements in resolution are theoretically achievable, suggesting that 2PE STED microscopy will permit nanoscale imaging, for instance, of neuronal structures located in relatively intact brain tissue.

GaN for THz sources

Paper 7945-35 of Conference 7945
Date: Monday, 24 January 2011
Time: 9:20 AM – 9:40 AM

Author(s): Michel Marso, Univ. du Luxembourg (Luxembourg)
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In this work we investigate the unique electrical and thermal performance of GaN to improve two different approaches to generate THz radiation. One method is the heterodyne photomixing, where the THz output power is restricted by the thermal and electrical limits of the conventionally used LT GaAs. The aim of our work is to increase the output power by replacing the LT GaAs with low-temperature grown GaN. In the second approach GaN-based ultrafast high electron mobility transistors are developed for use in a high power high frequency oscillator circuit that acts as source for a frequency multiplier chain.

Recent progress on high power optically pumped semiconductor lasers

Paper 7919-7 of Conference 7919
Date: Monday, 24 January 2011
Time: 11:00 AM – 11:30 AM

Author(s): Juan L. Chilla, Coherent, Inc. (United States)
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We have made steady progress since Coherent began working on Optically Pumped Semiconductor laser technology (OPS) in early 1997. Starting with the first commercially available solid state laser at 488 nm in 2001, we have translated the advantages of the OPS technology into products. These advantages include wavelength flexibility, broad pump tolerance, efficient spectral and spatial brightness conversion and high power scaling. In this presentation we will describe recent work on the development of multi-Watt visible lasers for scientific applications. These new lasers feature extremely low noise, as required for pumping ultrafast Ti:Sapphire lasers with Carrier Envelope Phase Stabilization.

Spatially resolved measurements of dynamic light scattering by Fourier domain OCT

Paper 7907-42 of Conference 7907
Date: Monday, 24 January 2011
Time: 11:10 AM – 11:30 AM

Author(s): Martin Hagen-Eggert, Medizinisches Laserzentrum Lübeck GmbH (Germany); Dierck Hillmann, Peter Koch, Thorlabs GmbH (Germany); Gereon Hüttmann, Univ. zu Lübeck (Germany)
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A method to make spatially resolved dynamic light scattering measurements with a Fourier-domain OCT system is presented. Fluctuations of signal intensity and phase, which are caused by Brownian motion are analysed by autocorrelation. Based on an ultrafast Fourier-domain OCT, this method can determine quantitatively spatially resolved diffusion properties, like the hydrodynamic diameter, of colloidal suspensions with high depth-resolution. Performance of this technique is demonstrated with polystyrene particle suspensions and compared to conventional DLS measurements. Applications may be found in the measurement of particle size distributions of inhomogeneous samples. Additionally, the method has the capability to be useful in clinical diagnostics.

Broadband bulk solid-state laser mode-locking based on carbon nanostructures

Paper 7937-26 of Conference 7937
Date: Monday, 24 January 2011
Time: 11:15 AM – 11:40 AM

Author(s): Fabian Rotermund, Ajou Univ. (Korea, Republic of)
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Carbon nanostructures such as carbon nanotubes (CNTs) and graphene are one of the most investigated nanomaterials due to their unique electric and optical properties. In recent years, their nonlinear optical characteristics were intensively investigated for photonic applications. In this talk we present recent progress on passive mode-locking of ultrafast bulk solid-state lasers using novel saturable absorbers based on single-walled carbon nanotubes (SWCNTs) and graphene. Important linear and nonlinear optical characteristics of SWCNT and graphene saturable absorbers essential for mode-locking and mode-locked operation of different bulk lasers in the spectral range between 1 and 2 ?m will be shown.

Subcellular recording of action potentials in cardiac myocytes with random access two-photon microscopy

Paper 7903-66 of Conference 7903
Date: Tuesday, 25 January 2011
Time: 11:35 AM – 11:50 AM

Author(s): Leonardo Sacconi, Raffaele Coppini, Cecilia Ferrantini, Jacopo Lotti, Chiara Tesi, Elisabetta Cerbai, Corrado Poggesi, Francesco S. Pavone, Univ. degli Studi di Firenze (Italy)
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In cardiac cells many membrane currents are heterogeneously distributed between the surface and t-tubule membranes. Here, we developed an ultrafast random access two-photon microscope capable to optical record fast membrane potential transients in multiple positions of the cell membrane with a ตm spatial resolution. Optical recording of AP waveforms were performed simultaneously in two different membrane sites: the surface and t-tubule membrane. Preliminary measurements indicate that APs from t-tubular membranes are likely regenerative and not electrotonically conducted, as indicated by the fast upstroke phase, whose raising rate did not differ from the surface sarcolemma.

Ultra-high-resolution and ultra-high-sensitive optical micro-angiography based on supercontinuum light source

Paper 7889-40 of Conference 7889
Date: Tuesday, 25 January 2011
Time: 11:45 AM – 12:00 PM

Author(s): Zhongwei Zhi, Lin An, Jia Qin, Ruikang K. Wang, Oregon Health & Science Univ. (United States)
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We demonstrate for the first time an ultrahigh resolution and ultrahigh sensitive optical micro-angiography (UHS-OMAG) system that is realized by a supercontinuum light source and an ultrafast CMOS camera. The broad band light source with a central wavelength at ~800nm, emitted from the supercontinuum light source, provides a ~2ตm coherence gate for the system. With the fast CMOS camera employed in the spectrometer operating at ~70 kHz line rate, we demonstrate that the detailed blood vessel networks, including capillaries, buried within the tissue bed can be visualized. We present the results obtained from the human finger nail fold and the mouse ear flap. The excellent system imaging performance shows a great potential of our system in the future biological imaging application.

All quantum dot based femtosecond VECSEL

Paper 7919-33 of Conference 7919
Date: Tuesday, 25 January 2011
Time: 2:45 PM – 3:00 PM

Author(s): Martin Hoffmann, Oliver D. Sieber, Wolfgang P. Pallmann, Valentin J. Wittwer, Yohan Barbarin, Thomas Südmeyer, Ursula Keller, ETH Zurich (Switzerland); Igor L. Krestnikov, Sergey S. Mikhrin, D. A. Livshits, Innolume GmbH (Germany); Graeme Malcolm, Craig Hamilton, M Squared Lasers Ltd. (United Kingdom)
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Using quantum well gain materials, ultrafast VECSELs have achieved higher output powers (2.1 W) and shorter pulses (60 fs) than any other semiconductor laser. Quantum dot (QD) gain materials offer a larger inhomogeneously broadened bandwidth potentially supporting shorter pulse durations. We demonstrate the first femtosecond QD-based VECSEL using a QD-SESAM for modelocking, obtaining 63 mW at 3.2 GHz in 780-fs pulses at 960 nm. In cw operation we obtained 5.2 W using an intra cavity diamond heat spreader, which has been the highest output power from a QD-VECSEL so far. Further power scaling is thus expected also for modelocked operation.

Optical pump-terahertz probe studies of AlGaN

Paper 7939-42 of Conference 7939
Date: Tuesday, 25 January 2011
Time: 5:00 PM – 5:20 PM

Author(s): Timothy M. Sweeney, Univ. of Oregon (United States); Grace D. Metcalfe, Gregory A. Garrett, Anand V. Sampath, Paul H. Shen, U.S. Army Research Lab. (United States); Hailin Wang, Univ. of Oregon (United States); Michael Wraback, U.S. Army Research Lab. (United States)
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We report on ultrafast optical pump and terahertz probe studies of free-carrier dynamics in AlGaN materials grown with and without nano-scale compositional inhomogeneities (NCI). We observe an initial fast decrease of the transmitted THz signal in both AlGaN samples due to the generation of photoexcited free-carriers. The NCI AlGaN material shows a subsequent fast decrease in THz absorption, as compared to the NCI-free AlGaN. The faster decay time in the NCI AlGaN sample could be due to the transfer of free-carriers into NCI states from the AlGaN matrix as well as exciton formation and carrier recombination.

Designer pulses for optimal ablation

Paper 7920-29 of Conference 7920
Date: Wednesday, 26 January 2011
Time: 8:00 AM – 8:30 AM

Author(s): Razvan I. Stoian, Jean-Philippe Colombier, M. Guillermin, Florence Garrelie, Eric Audouard, Lab. Hubert Curien, CNRS, Univ. de Lyon, Univ. Jean Monnet Saint-Etienne (France)
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Determining thermodynamic trajectories is an essential factor for controlling the nature and the energetic characteristics of the ablation products following laser irradiation of materials on ultrafast scales. In this respect designing the energy delivery rate using pulse shaping methods in the temporal domain is a powerful way for controlling the excitation and thermodynamic relaxation of the material. Using experimental and theoretical adaptive loops based on hydrodynamic codes we indicate the shape of optimal pulses required to reach extreme thermodynamic states at limited energy input. The results are interesting for remote spectroscopy applications and generation of nanoparticles.

Hybrid MT-OCM imaging platform for in-vivo tissue imaging

Paper 7889-62 of Conference 7889
Date: Wednesday, 26 January 2011
Time: 9:45 AM – 10:00 AM

Author(s): Antti Isomäki, Lars Thrane, Henning E. Larsen, Technical Univ. of Denmark (Denmark); Karsten Koenig, Univ. des Saarlandes (Germany); Peter E. Andersen, Technical Univ. of Denmark (Denmark)
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We report on a combined multiphoton tomography (MT) and optical coherence microscopy (OCM) imaging platform. The combination of the two optical imaging modalities allows for multi-modal cellular and molecular diagnostic imaging. The system is based on a commercial multiphoton tomograph which is modified to accommodate an OCM unit. Two different OCM unit designs are considered here. The first one is using a separate broadband light source at 1.3 micron wavelength range. The second approach takes advantage of sub-12 fs pulses from a Ti:sapphire laser. Ultrafast broadband pulses enable high resolution optical biopsy with simultaneous MT and OCM image acquisition.

Fiber-optic Cherenkov radiation excited by few-cycle pulses

Paper 7937-57 of Conference 7937
Date: Wednesday, 26 January 2011
Time: 9:55 AM – 10:20 AM

Author(s): Guoqing Chang, Li-Jin Chen, Franz Kaertner, Massachusetts Institute of Technology (United States)
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Fiber-optic Cherenkov radiation (CR) has emerged as a wavelength conversion technique to achieve isolated spectrum in the visible wavelength range. Most published results have reinforced the impression that CR forms narrowband spectrum with poor efficiency. We have both numerically and experimentally investigated CR in the few-cycle pulse regime. Our results demonstrated that CR, when pumped with 10 fs pulses of more than 200 pJ pulse energy, exhibits high conversion efficiency (>40%), broad bandwidth (>50 nm), and low threshold (<100 pJ for pulse energy). These three merits allow achieving broadband visible-wavelength spectra from low-energy ultrafast sources which opens up new applications.

High-speed multiple-process imaging using FLIM-FRET for complex and dynamic live-cell studies

Paper 7904-35 of Conference 7904
Date: Wednesday, 26 January 2011
Time: 3:00 PM – 3:20 PM

Author(s): Romain Laine, Anca Margineanu, Sunil Kumar, Gordon T. Kennedy, David M. Grant, James A. McGinty, Clifford B. Talbot, David Carling, Christopher W. Dunsby, Mark A. Neil, Imperial College London (United Kingdom); Matilda Katan-Muller, The Institute of Cancer Research (United Kingdom); Alessandro Sardini, Imperial College Healthcare NHS Trust (United Kingdom); Paul M. W. French, Imperial College London (United Kingdom)
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We report the first high-speed optically sectioned FLIM microscope capable of multiplexing FRET readouts for fixed or live cell studies. This is implemented using a Nipkow spinning disk microscope and rapid wide-field time-gated FLIM with tunable ultrafast excitation. The fully automated spectral channel multiplexing, z-stack and time lapse imaging permit multiple cellular signalling events to be followed in real time with FLIM acquisitions reading out FRET in < 5 s. Multiplexed FLIM was demonstrated by reading out calcium transients in live cells following ionomycin stimulation simultaneously using a transfected FRET calcium sensor (TNL15 and a calcium dye (FluoForte(TM)).

Optical properties and applications of liquid crystals in the THz frequency range

Paper 7955-25 of Conference 7955
Date: Wednesday, 26 January 2011
Time: 4:30 PM – 5:00 PM

Author(s): Ci-Ling Pan, National Tsing Hua Univ. (Taiwan)
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In the past decade, THz studies ranging from investigations of ultrafast dynamics in materials to medical, environmental sensing and imaging have been actively explored. For these and future applications in THz communication and surveillance, quasi-optic components such as phase shifters are indispensable. The birefringence of liquid crystal (LC) is well known and extensively utilized for the manipulation of optical radiation in the visible and near-infrared range. Recently, there have been increasing interests in the study of liquid-crystal-based devices for application in the sub-millimeter wave or THz frequency range. In this paper, we review recent available optical constants of selected liquid crystals in this important frequency range and recent advances in liquid crystal THz optic and photonic devices.

Diffusion-sensitive Fourier-domain optical coherence tomography

Paper 7889-82 of Conference 7889
Date: Wednesday, 26 January 2011
Time: 5:15 PM – 5:30 PM

Author(s): Martin Hagen-Eggert, Medizinisches Laserzentrum Lübeck GmbH (Germany); Dierck Hillmann, Peter Koch, Thorlabs GmbH (Germany); Gereon Hüttmann, Univ. zu Lübeck (Germany)
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Diffusion-sensitive OCT (DS-OCT) is presented as a functional extension to OCT. Fluctuations of signal intensity and phase, which are caused by Brownian motion are analysed by autocorrelation. Based on an ultrafast Fourier-domain OCT, DS-OCT can determine quantitatively spatially resolved diffusion properties, like the hydrodynamic diameter, of colloidal suspensions with high depth-resolution. Performance of DS-OCT is demonstrated with polystyrene particle suspensions and compared to conventional DLS measurements. Applications for DS-OCT may be found in the measurement of particle size distributions of inhomogeneous samples. Additionally, the method has the capability to be useful in clinical diagnostics

3D adaptive spatio-temporal control of laser-induced refractive index changes in optical glasses

Paper 7921-15 of Conference 7921
Date: Thursday, 27 January 2011
Time: 8:50 AM – 9:20 AM

Author(s): Razvan I. Stoian, Lab. Hubert Curien (France)
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Ultrafast laser photoinscription has become a viable method for 3D processing of dielectric materials based on nonlinear energy confinement. As the processing results depend on the spatio-temporal character of interaction, we report on the use of adaptive self-improving optics in spatio-temporal domains for upgrading laser-induced refractive index engineering with respect to the quality of the structural change and the time-effectiveness of interaction. New laser-matter synergies are created and concepts of parallel processing and wavefront engineering are explored. Additionally, taking advantage on laser-induced self-arrangement on the nanoscale we design polarization sensitive devices and indicate particular light propagation properties in 3D structures.

Nonlinear parametric processes in photonic crystal nanostructures

Paper 7942-16 of Conference 7942
Date: Thursday, 27 January 2011
Time: 1:00 PM – 1:30 PM

Author(s): Chee Wei Wong, James F. McMillan, Chad A. Husko, Jiangjun Zheng, Ying Li, Jie Gao, Jing Shu, Serdar Kocaman, Tingyi Gu, Mehmet Aras, Columbia Univ. (United States)
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We examine the control of photons in engineered photonic crystal nanostructures. First, we demonstrate the strong control of dispersion and localization in photonic crystals, leading to state-of-the-art slow-light structures, ultrahigh-Q nanocavities and zero-index superlattices. Coherent interactions in such nanostructures lead to recent observations of an optical analogue to electromagnetically-induced-transparency, and lasing cooling in chip-scale cavity optomechanics. Second, we report our studies in nonlinear optics through the tight field confinement and long photon lifetimes in photonic crystal structures. Examples include slow-light enhanced four-wave mixing, soliton dynamics and pulse compression (together with Thales), Raman scattering, and single-photon-level nonlinearities for quantum non-demolition. Designed from first principles, these chip-scale advances have implications in ultrafast optics and communications, optical signal processing and quantum information sciences.

Femtosecond laser micro/nano patterning of biological materials

Paper 7925-5 of Conference 7925
Date: Sunday, 23 January 2011
Time: 10:50 AM – 11:20 AM

Author(s): Costas P. Grigoropoulos, Hojeong Jeon, Univ. of California, Berkeley (United States); Hirofumi Hidai, Univ. of California, Berkeley (Japan); David J. Hwang, Univ. of California, Berkeley (United States)
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This talk aims at presenting recent work at the Laser Thermal Laboratory on the microscopic and nanoscale laser modification of biological materials using ultrafast laser pulses. We have devised a new method for fabricating high aspect ratio patterns of varying height by using two-photon polymerization process in order to study contact guidance and directed growth of biological cells. Studies using NIH-3T3 and MDCK cells indicate that cell morphology on fiber scaffolds is influenced by the pattern of actin microfilament bundles. Cells experienced different strength of contact guidance depending on the ridge height. Cell morphology and motility was investigated on micronscale anisotropic cross patterns and parallel line patterns having different aspect ratios. A significant effect on cell alignment and directionality of migration was observed. Cell morphology and motility were influenced by the aspect ratio of the cross pattern, the grid size, and the ridge height. Cell contractility was examined microscopically in order to measure contractile forces generated by individual cells on self-standing fiber scaffolds. We have also introduced a method for generating user-defined nanopatterns of cell adhesion ligands by ablating an ultrathin protein adsorption resistant poly(ethylene glycol) brush layer using focused femtosecond laser pulses to expose an underlying adhesive substrate. The ablated regions were modified with peptides designed to engage with specific receptors. We were able to generate nanometer scale regions of cell adhesive peptides, while independently controlling feature size and spacing, hence allowing direct specification of the number and area of focal adhesion patterns. We have also conducted experiments to determine the effect of laser-induced nanoscale laser topography on cell adhesion.

Advancements in photomixing and photoconductive switching for THz spectroscopy and imaging

Paper 7938-1 of Conference 7938
Date: Thursday, 27 January 2011
Time: 8:00 AM – 8:30 AM

Author(s): Elliott R. Brown, Wright State Univ. (United States) and Physical Domains, LLC (United States)
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Ultrafast photoconductive devices have been an important breakthrough in THz technology during the past two decades. Photoconductive switches have become the workhorse in moderate-resolution time-domain systems, and photomixers have been widely implemented in high-resolution spectrometers of various types. The primary photoconductive material has been low-temperature-grown GaAs. More recently, this has been rivaled by ErAs-GaAs: a nanocomposite consisting of ErAs nanoparticles embedded in a GaAs matrix. ErAs-GaAs photomixers have produced very useful THz output power levels between 1.0 and 10.0 microwatt when pumped by low-cost DFB lasers operating around 780 nm. ErAs-GaAs photoconductive switches have produced average output power approaching 1 mW, and peak power exceeding 1 W when pumped by frequency-doubled fiber model-locked lasers. The photomixer performance has been utilized in the first U.S. commercial THz photomixing spectrometer which has already been demonstrated on a variety of interesting materials including polar vapors, solid explosives, polysaccharides, nucleic acids, and nonlinear-optical crystals. The photoconductive switch performance has been utilized in a THz impulse radar having a broadband power spectrum centered at around 500 GHz, and a relatively simple gated-receiver to provide pulse averaging and noise reduction. The impulse radar has been used for several applications in biomedical imaging, such as imaging of skin burns, skin cancer, and the ocular cornea.


Multiphoton endoscopy based on a mode-filtered single-mode fiber

Paper 7903-95 of Conference 7903
Date: Sunday, 23 January 2011
Time: 5:30 PM

Author(s): Sucbei Moon, Gangjun Liu, Zhongping Chen, Beckman Laser Institute and Medical Clinic (United States)
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We present a new low-nonlinearity fiber of mode-filtered single-mode fiber (MF-SMF) for a flexible beam delivery of ultra-short pulses used in the application of multi-photon endoscopy. In our scheme, a few-mode fiber of a relatively large core equips a mode filtering means in the middle of the beam transmission to reject the high-order modes selectively. We demonstrated a scanning catheter two-photon endoscope at the 1.06-um band to show the attractive features of our scheme. Since our method is based on the conventional low-cost fiber technology, the MF-SMF is very easy to handle, especially in fiber splicing and connectorizing.

Spectral decomposition of multicolor imaging in multifocal multiphoton microscopy

Paper 7903-103 of Conference 7903
Date: Sunday, 23 January 2011
Time: 5:30 PM

Author(s): Jae-Won Cha, Jerry L. Chen, Elly Nedivi, Peter T. C. So, Massachusetts Institute of Technology (United States)
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Multifocal multiphoton microscopy (MMM) is known as one of the best methods for the high throughput neurobiological imaging. In addition to improving imaging speed, spectral resolved imaging is further required to study both structural and synaptic dynamics during plasticity, and we have developed spectral resolved MMM. However, due to the spectral overlap of the emission spectrums, computational spectral unmixing is often required. The success of spectral unmixing is often limited by the inherent Poisson noise in the image data. We propose Poisson noise removal before the spectral unmixing to improve the outcome of spectrally overlap signals.

Multiphoton imaging for deep-tissue penetration and clinical endoscopy

Paper 7891-16 of Conference 7891
Date: Tuesday, 25 January 2011
Time: 8:30 AM – 9:00 AM

Author(s): Chris Xu, Cornell Univ. (United States)
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The main advantages of multiphoton microscopy (MPM) lie in two areas of applications: (1) imaging deep into scattering tissues, and (2) imaging intrinsic fluorescence and harmonic generation, particularly for in vivo investigations. The intrinsic excitation localization and the longer wavelength used enable MPM to image deep into scattering biological specimens. Nonlinear excitation allows the use of near IR wavelength to excite fluorophores that normally absorb in the UV or deep UV region, enabling imaging of intrinsic fluorescence without the limitation of UV photodamage. Nonlinear harmonic generation also provides a unique contrast mechanism for MPM. Multiphoton imaging may potentially become a useful tool for clinical diagnosis. In this paper, we present our efforts in improving the penetration depth of MPM and the development of a multiphoton endoscope for imaging intrinsic tissue fluorescence and harmonic generation in vivo, with a main focus on instrument design and optimization

Long-term, time-lapse, multimodal microscopy for tracking cell dynamics in live tissue

Paper 7902-4 of Conference 7902
Date: Saturday, 22 January 2011
Time: 9:30 AM – 9:50 AM

Author(s): Benedikt W. Graf, Eric J. Chaney, Maria Carmen Valero Quiros, Marina Marjanovic, Marni D. Boppart, Stephen A. Boppart M.D., Univ. of Illinois at Urbana-Champaign (United States)
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High speed intravital microscopy has emerged as an essential tool for studying cellular dynamics in live tissue. However the timescales that tissue can be continuously observed is limited to several hours. We present methods for observing long term cellular dynamics in live tissue based on three-dimensional registration of time-lapse intravital microscopy images. These methods are applied for in vivo tracking of bone-marrow derived GFP-labeled stem cells in mouse skin following bone marrow transplants from GFP donors into wildtype hosts. This enables tracking of these cells after local cutaneous injury, and for investigating the role of skin stem cells in wound healing.

Fiber-based combined optical coherence and multiphoton microscopy

Paper 7892-9 of Conference 7892
Date: Saturday, 22 January 2011
Time: 11:30 AM – 11:50 AM

Author(s): Gangjun Liu, Zhongping Chen, Beckman Laser Institute and Medical Clinic (United States)
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This manuscript demonstrates a multimodal imaging system which combined multiphoton microscopy (MPM) imaging modality with Fourier domain (FD) optical coherence microscopy (OCM) modality. The system used a single fiber femtosecond laser as the light source for both MPM and OCM modality. The femtosecond fiber laser has a central wavlength of 1.03um and a pulse width of 120fs. The systems used fiber based devices for both MPM and OCM. The MPM and OCM shared the same excitation light path. The excitation light was delivered with the core of a dual-clad fiber. The MPM signal was collected by the clad of the dual-clad fiber. The FD OCM used a home-built InGaAs detector array spectrometer.

High-resolution multimodal clinical multiphoton tomography of skin

Paper 7883A-12 of Conference 7883A
Date: Saturday, 22 January 2011
Time: 1:40 PM – 2:00 PM

Author(s): Karsten Koenig, Saarland Univ. (Germany)
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CE-marked clinical multiphoton systems for 5D imaging of human skin with subcellular resolution, 10 nm spectral resolution, and 250 ps temporal resolution are in clinical use in Europe, Asia, and Australia. These tomographs provide optical biopsies with submicron resolution based on two-photon excited autofluorescence (NAD(P)H, flavoproteins, keratin, elastin, melanin, porphyrins) and second harmonic generation by collagen. Photons are collected by time-resolved single photon counting. The novel tomographs are employed for the early detection of malignant melanoma, atopic dermatitis, and the analysis of treatment effects as well as for the intratissue detection of cosmetical and pharmaceutical components including sunscreen nanoparticles. Novel developments include the combination with ultrasound, optical coherence tomography, CARS, and diffuse reflectance.

Clinical Multiphoton Tomography

Date: Saturday, 22 January 2011
Time: 8:25 PM – 8:35 PM

Author(s):
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Karsten Koenig, Saarland Univ. and JenLab GmbH (Germany)

Intravital multiphoton tomography as an appropriate tool for non-invasive in-vivo analysis of human skin affected with atopic dermatitis

Paper 7883A-26 of Conference 7883A
Date: Sunday, 23 January 2011
Time: 9:00 AM – 9:20 AM

Author(s): Volker Huck, Westfälische Wilhelms-Univ. Münster (Germany); Christian Gorzelanny, Ruprecht-Karls-Univ. Heidelberg (Germany); Kai Thomas, Westfälische Wilhelms-Univ. Münster (Germany); Martin Schwarz, Iris Riemann, Fraunhofer-Institut für Biomedizinische Technik (Germany); Christian Mess, Verena Niemeyer, Ruprecht-Karls-Univ. Heidelberg (Germany); Thomas A. Luger, Westfälische Wilhelms-Univ. Münster (Germany); Karsten Koenig, JenLab GmbH (Germany); Stefan W. Schneider, Ruprecht-Karls-Univ. Heidelberg (Germany)
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Increasing incidence of Atopic Dermatitis (AD) has been noted in the past years. An impaired physical skin barrier predispose for the development of AD. Within a clinical in vivo study we focused on the epidermal cell metabolism and barrier formation in 20 AD affected patients in comparison to healthy subjects. Measurement of fluorescence life-time of NADH provides access to the metabolic state of skin. Therefore, we facilitate the non-invasive investigation of epidermis in the longitudinal course of AD therapy. Our findings allow a deeper understanding of the individual disease development and the improved management of therapeutic intervention in clinical application.

New developments in clinical multiphoton tomography (Keynote Presentation)

Paper 7903-3 of Conference 7903
Date: Sunday, 23 January 2011
Time: 9:35 AM – 10:05 AM

Author(s): Karsten Koenig, Univ. des Saarlandes (Germany)
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The multiphoton tomographs DermaInspect™ and MPTflex™ are novel clinical skin imaging devices using a near-infrared femtosecond laser source. Non-linear excitation allows to detect natural endogenous fluorophores inside human skin such as NAD(P)H, flavins, elastin, collagen, melanin, keratin, and porphyrins down to a tissue depth of 200 ตm without applying any contrast agents. Individual intratissue cells, intracellular mitochondria, melanosomes, and the morphology of the nuclei as well as extracellular matrix elements can be imaged. In vivo 5D imaging can be realized based on spectral fluorescence lifetime imaging. So far, more than 1,000 patients and volunteers in Europe, Asia, and Australia have been investigated with these novel molecular imaging tools. Current developments include the production of multimodal hybrid systems such as the combination with ultrasound, optical coherence tomography, diffuse reflectance, and CARS.

In-vivo multiphoton imaging of collagen remodeling after micro-ablative fractional rejuvenation

Paper 7883A-31 of Conference 7883A
Date: Sunday, 23 January 2011
Time: 10:50 AM – 11:10 AM

Author(s): Riccardo Cicchi, Dimitrios Kapsokalyvas, Michela Troiano, Piero Campolmi, Cristiano Morini, Alessandro Cosci, Daniela Massi, Torello Lotti, Francesco S. Pavone, Univ. degli Studi di Firenze (Italy)
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Two-photon excited fluorescence and second-harmonic generation microscopy were used in combination to follow-up collagen remodeling after laser micro ablative rejuvenation. Treated regions of volunteers were imaged with multiphoton microscopy before and after treatment, and we found a strong age-dependence of the treatment effectiveness. Quantification of the amount of newly produced collagen and its organization were performed by means of two image-analysis methods. The obtained results demonstrate the performance of laser fractional micro ablative rejuvenation without the need of an invasive biopsy as well as the wide range of applications for multiphoton microscopy in clinical dermatology.

Epifluorescence light collection for multiphoton microscopic endoscopy

Paper 7893-10 of Conference 7893
Date: Sunday, 23 January 2011
Time: 11:20 AM – 11:40 AM

Author(s): Christopher M. Brown, David R. Rivera, Chris Xu, Watt W. Webb, Cornell Univ. (United States)
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Maximizing light collection from multiphoton microscopy endoscopes remains a challenge, as weak nonlinear emissions and light scattering in tissue hamper light collection. In this experiment, we investigate collection of scattered and unscattered light from a tissue phantom. Experimentally, the ratio of detected epifluorescent unscattered to scattered light decreased from 13:1 to 0.76:1 on increasing the imaging depth from 0 to 200 um in a bladder tissue phantom. Based on these results, a light collection scheme employing a dual clad fiber for collection of unscattered light as well as an optical fiber array for collection of scattered emission light is proposed.

In-vivo optical investigation of psoriasis

Paper 7883A-33 of Conference 7883A
Date: Sunday, 23 January 2011
Time: 11:30 AM – 11:50 AM

Author(s): Dimitrios Kapsokalyvas, Riccardo Cicchi, Nicola Bruscino, Alessandro Cosci, Daniela Massi, Torello Lotti, Francesco S. Pavone, Univ. degli Studi di Firenze (Italy)
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Psoriasis is an autoimmune disease of the skin. Cases of psoriasis were investigated in vivo with optical means. A Polarization Multispectral Dermoscope was employed for the macroscopic observation. Features such as the 'dotted' blood vessels pattern were observed. Microscopic observation was performed with a custom made multiphoton microscope. Imaging extended from the surface of the lesion down to the papillary dermis, at a depth of 200 ตm. Morphological, spectral and fluorescence lifetime measurements were performed and the results of psoriatic lesions were compared to healthy skin. The in-vivo morphologic observations on psoriasis correlate strongly with the ex vivo histopathologic findings.

Latest advances in ultra-fast laser sources for multiphoton microscopy

Paper 7903-19 of Conference 7903
Date: Sunday, 23 January 2011
Time: 3:50 PM – 4:05 PM

Author(s): Philip G. Smith, Spectra-Physicsฎ, a Newport Corp. Brand (United States)
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The advent of compact, fully automated, and widely wavelength-tunable ultrafast oscillators has triggered an explosive growth in their use in a broad array of multiphoton imaging techniques. Over the past decade laser manufacturers have constantly improved the performance characteristics of these sources to meet the requirements of the user community. We will review the latest advances at Newport / Spectra-Physics in this field and discuss new ways of optimizing key parameters for efficient deep-tissue fluorescence generation, including turn-key, automated second order dispersion compensation that allows for optimization of the pulse width at the sample over a wide wavelength range, without compromising beam pointing and other critical beam parameters.

Autocorrelation of femtosecond VUV pulses using multiphoton ionization

Paper 7915-15 of Conference 7915
Date: Sunday, 23 January 2011
Time: 4:00 PM – 4:20 PM

Author(s): Shoichi Kubodera, Wataru Nagaya, Hironari Zushi, Masanori Kaku, Masahito Katto, Univ. of Miyazaki (Japan)
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We have been developing a simple and versatile autocorrelator utilizing multiphoton ionization of gaseous media to characterize femtosecond laser pulses, which could be used in the wide wavelength regions between infrared (IR) and vacuum ultraviolet (VUV). Femtosecond IR laser pulses were characterized by autocorrelated electron signals of rare gases. Although Xe should have required nine photons to be ionized with the IR laser at 882 nm, the four-photon ionization was observed. By using the fourth-order correlation function, the pulse width of 173 fs was determined for the 882 nm laser, which agreed with that measured with a two-photon autocorrelator.

Advances in lasers for multiphoton biological imaging

Paper 7903-20 of Conference 7903
Date: Sunday, 23 January 2011
Time: 4:05 PM – 4:20 PM

Author(s): David P. Armstrong, Coherent, Inc. (United States)
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Key to future advances in multiphoton biological imaging is the ability to work with a wider range of fluorophores, to image deeper into samples and to minimize sample damage. In terms of laser characteristics, these requirements translate into wider tuning range and sufficient excitation (average and peak power). This paper explores the advances in tunable ultrafast sources, both laser and OPO, to meet these goals and thus power the next generation of MPE instrumentation.

Compact ultrafast semiconductor disk laser for nonlinear imaging in living organisms

Paper 7903-99 of Conference 7903
Date: Sunday, 23 January 2011
Time: 5:30 PM

Author(s): Rodrigo A. Aviles-Espinosa, ICFO - Instituto de Ciencias Fotónicas (Spain); Giorgos Filippidis, Foundation for Research and Technology-Hellas (Greece); Craig Hamilton, Solus Technologies Ltd. (United Kingdom); Graeme Malcolm, M Squared Lasers Ltd. (United Kingdom); Thomas Südmeyer, Yohan Barbarin, Ursula Keller, ETH Zurich (Switzerland); David Artigas-García, Univ. Politècnica de Catalunya (Spain); Pablo Loza-Alvarez, ICFO - Instituto de Ciencias Fotónicas (Spain)
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Expensive, bulky and complex Ti:sapphire-based ultrafast laser systems have prevented the wide-spread introduction of nonlinear microscopy in biomedical applications. We present the use of a compact semiconductor disk laser (140x240x70 mm) passively modelocked with a quantum-dot SESAM to produce nonlinear images of living C. elegans. The laser delivers 1.5 ps pulses at 500 MHz having an average output power of 287 mW (peak power of 0.5 kW). Its center wavelength located at 965 nm is ideally suited for two-photon excitation of the widely used GFP marker. This non-expensive, turn-key compact laser is ideal for portable nonlinear biomedical imaging devices.

Electroporation-induced nanopores in primary neurons studied by means of SHG microscopy

Paper 7903-113 of Conference 7903
Date: Sunday, 23 January 2011
Time: 5:30 PM

Author(s): Dobryna Zalvidea, Enric Claverol-Tinture, Institute for Bioengineering of Catalonia (Spain)
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Electroporation, the generation of transient nanopores in the cell membrane due to a pulsed external electric field, was studied at the millisecond scale with subwavelength resolution. We introduce a novel nonlinear optical technique, pattern-resolved second harmonic generation microscopy (pr-SHG Microscopy), which is sensitive to a fast radiation pattern redistribution of second harmonic signals. We designed a new collection system for a commercial multiphoton microscope. By using phase-array analysis, we calculate second harmonic pattern distribution generated by an arrangement of scatterers during transient population of pores for different locations at the cell.

Nonlinear miniaturized microscope with spectral detection for in-vivo tissue imaging

Paper 7903-114 of Conference 7903
Date: Sunday, 23 January 2011
Time: 5:30 PM

Author(s): Johan van Voskuilen, Jerfey van Weelden, Oleg Nadiarnykh, Utrecht Univ. (Netherlands); Giju Thomas, Henricus J. C. M. Sterenborg, Erasmus MC (Netherlands); Hans C. Gerritsen, Utrecht Univ. (Netherlands)
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A nonlinear miniaturized microscope is presented designed for nonlinear optical biopsies, which uses resonant scanning. The scanner is fiber coupled to the microscope using a double clad photonic crystal fiber. This facilitates signal guiding of single-mode infrared excitation and broadband multimode visible emission. Group velocity dispersion by the fiber is pre-compensated with a grating pair. Emission is detected using a custom built spectrograph with a sensitive EMCCD. The nonlinear excitation provides contrast without applying stains in living tissue. Signals are detected from, amongst others, auto-fluorescence of NADH, FAD, melanin, and SHG of collagen. Tests and results on tissue are shown.

Quantifying the surface chemistry of porous biomaterials by two-photon microscopy

Paper 7903-97 of Conference 7903
Date: Sunday, 23 January 2011
Time: 5:30 PM

Author(s): Dimitrios S. Tzeranis, Ioannis V. Yannas, Peter T. C. So, Massachusetts Institute of Technology (United States)
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This work presents a new method for quantifying in situ the surface chemistry (type and density of ligands recognized by cell adhesion receptors) of biomaterials, and therefore the effect of the insoluble matrix on the interacting cells. The ligands for a particular cell adhesion receptor are labeled by a fluorescent biomarker that imitates the receptor's binding characteristics. The labeled biomaterial is imaged by multiphoton microscopy, and the surface density of ligands is estimated by Bayesian image processing. The method is demonstrated by measuring the surface density of ligands for collagen-binding integrins on scaffolds used in clinical regenerative medicine applications.

Spectral characteristics of two-photon autofluorescence and second-harmonic generation from human skin in vivo

Paper 7883A-37 of Conference 7883A
Date: Sunday, 23 January 2011
Time: 5:30 PM

Author(s): Hans G. Breunig, Karsten Koenig, JenLab GmbH (Germany)
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We have modified the certified multiphoton tomograph DermaInspect (JenLab GmbH) to record, in addition to spatially resolved signal intensities, the complete spectral content of multiphoton microscopy signals integrated over the sampled area. In particular, the in vivo-emission characteristics of main endogenous skin fluorophores like keratin, NAD(P)H, melanin, collagen and elastin are investigated for a broad range of laser excitation wavelengths and compared to known spectra of purified substances. The classification of the signals is further supported by analysis of in vivo fluorescence lifetime imaging (FLIM). Furthermore, the possibility to detect nano particles of sunscreens on skin in vivo is discussed.

Two-photon selective plane illumination microscopy (2p-SPIM) in living biological samples

Paper 7903-93 of Conference 7903
Date: Sunday, 23 January 2011
Time: 5:30 PM

Author(s): Jonathan A. Palero, Susana I. C. O. Santos, ICFO - Instituto de Ciencias Fotónicas (Spain); David Artigas-García, Univ. Politècnica de Catalunya (Spain); Pablo Loza-Alvarez, ICFO - Instituto de Ciencias Fotónicas (Spain)
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The past two decades saw the emergence of two photon (2p) laser-scanning microscopy as a powerful imaging tool for thick tissue imaging owing to its inherent optical sectioning capability and deep penetration. The drawback, however, of this imaging technique is its relatively slow image acquisition rate. In this study, we demonstrate a simple scanless two-photon imaging technique based on selective plane illumination microscopy (SPIM). We show the relative simplicity of the experimental setup and demonstrate application of 2p-SPIM to depth-resolved in vivo biological imaging.

Influence of laser parameters and staining on femtosecond laser-based intracellular nanosurgery

Paper 7897-3 of Conference 7897
Date: Monday, 24 January 2011
Time: 8:50 AM – 9:10 AM

Author(s): Kai Kuetemeyer, Rachid Rezgui, Holger Lubatschowski, Alexander Heisterkamp, Laser Zentrum Hannover e.V. (Germany)
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Femtosecond laser-based intracellular nanosurgery has become an important tool in cell biology, albeit the mechanisms are largely unknown. Here, we present our experimental study on the influence of laser parameters and staining on the intracellular ablation threshold in the low-density plasma regime. We found that the ablation effect of pulse trains resulted from the accumulation of single-shot multiphoton-induced photochemical effects finished within a few nanoseconds. Furthermore, fluorescence staining of subcellular structures before surgery significantly decreased the ablation threshold. Based on our findings, we propose that dye molecules are the major source for providing seed electrons for the ionization cascade.

CARS module for multimodal microscopy

Paper 7903-31 of Conference 7903
Date: Monday, 24 January 2011
Time: 11:13 AM – 11:25 AM

Author(s): Ruben Zadoyan, Tommaso Baldacchini, Chun-Hung Kuo, John L. Carter, David Ocepek, Newport Corp. (United States)
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We describe a stand alone CARS module allowing upgrade of a two-photon microscope with CARS modality. The Stokes beam is generated in a commercially available PCF using fraction of the excitation laser power. We demonstrate functionality of the device on examples of multimodal images of several biological and non-biological samples. We also present results of studies where we used CARS modality to monitor in real time the process of fabrication of nanostructures by two-photon polymerization (CARS movie will be presented).

Triply surface-plasmon resonant four-wave mixing imaging of gold nanoparticles

Paper 7911-33 of Conference 7911
Date: Monday, 24 January 2011
Time: 1:30 PM – 1:50 PM

Author(s): Francesco Masia, Wolfgang Langbein, Peter Watson, Paola Borri, Cardiff Univ. (United Kingdom)
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We demonstrate a novel multiphoton microscopy technique not relying on (hence not limited by) fluorescence emission, which exploits four-wave mixing (FWM) of gold nanoparticles (GNPs) in resonance with their surface Plasmon. The coherent, transient and resonant nature of this signal allows its detection free from the background limiting other contrast methods for GNPs. We show high-contrast high-resolution imaging of gold-labels down to 5nm size in Golgi structures of HepG2 cells. We also show sensitivity to single GNPs. By detecting the transient nonlinearity using 100fs pulses with adjustable delay we gain fundamental insights into the physical processes creating FWM.

Combining multiphoton and CARS microscopy for skin imaging

Paper 7903-42 of Conference 7903
Date: Monday, 24 January 2011
Time: 2:57 PM – 3:09 PM

Author(s): Hans G. Breunig, JenLab GmbH (Germany); Karsten Koenig, Univ. des Saarlandes (Germany)
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Coherent anti Stokes Raman scattering (CARS) microscopy enables highly sensitive, label-free imaging thus providing the possibility of three dimensional imaging of tissue and skin. We present measurement results of combined epi CARS and multiphoton microscopy, hence, label-free imaging of skin with both chemical discrimination and subcellular resolution. In particular, we show how epi-CARS microscopy is utilized to image lipid-rich structures inside the skin, preparing for a combined multiphoton and CARS imaging modality for biomedical research and skin imaging.



Differential-CARS microscopy with linearly chirped femtosecond laser pulses

Paper 7903-50 of Conference 7903
Date: Monday, 24 January 2011
Time: 4:53 PM – 5:05 PM

Author(s): Wolfgang Langbein, Israel Rocha-Mendoza, Peter Watson, Paola Borri, Cardiff Univ. (United Kingdom)
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We demonstrate frequency differential CARS (D-CARS) using femtosecond laser pulses linearly chirped by glass elements of high group-velocity dispersion. By replicating the Pump-Stokes pair into a pulse train at twice the laser repetition rate, and controlling the instantaneous frequency difference by glass dispersion, we adjust the Raman frequency probed by each pair in an intrinsically stable way. The resulting CARS intensities are detected simultaneously by a single photomultiplier as sum and difference using lock-in detection. We demonstrate imaging of polymer beads and living cells with strongly suppressed non-resonant background. We also show D-CARS using a single femtosecond laser source.

Multiphoton luminescence of gold nanorods upon excitation with wavelengths away from their absorption maxima

Paper 7910-21 of Conference 7910
Date: Monday, 24 January 2011
Time: 5:20 PM – 5:40 PM

Author(s): Naveen K. Balla, Colin J. R. Sheppard, National Univ. of Singapore (Singapore); Peter T. C. So, Massachusetts Institute of Technology (United States)
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Here we compare multiphoton photon luminescence properties of gold nanorods when excited at wavelengths around 800 nm and 1200 nm. Excitation with wavelengths around 1200 nm has certain advantages like lower heating of the particles and hence prolonged durations of imaging. Other advantage is the ability to collect emission in the near infrared regions (NIR) up to 800 nm which is not possible when using excitation wavelengths around 800 nm. These features are good for deep tissue imaging. One disadvantage of this approach is lower luminescence intensity.

Sub-100-nm material processing with sub-15-femtosecond picojoule near-infrared laser pulses

Paper 7903-54 of Conference 7903
Date: Tuesday, 25 January 2011
Time: 8:00 AM – 8:20 AM

Author(s): Karsten Koenig, Aisada A. Uchugonova, Martin H. Straub, Huijing Zhang, Maziar Afshar, Dara Feili, Helmut Seidel, Univ. des Saarlandes (Germany)
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Ultrabroad band in situ 12 femtosecond near infrared laser pulses at transient TW/cm2 intensities and low picojoule pulse energies (mean powers < 20 mW at 85 MHz repetition rate) have been used to perform 3D material nanoprocessing based on multiphoton ionization and plasma formation. Cut sizes of sub-wavelength, sub-100 nm which is far beyond the Abbe diffraction have been realized without any collateral damage effect in silicon wafers, photoresists, glass, metals, and biological targets. Acknowledgments: The authors wish to thank the German Science Foundation (Key Program 1327) for financial support.

Nanosurgery with near-infrared femtosecond and picosecond laser pulses

Paper 7903-55 of Conference 7903
Date: Tuesday, 25 January 2011
Time: 8:20 AM – 8:40 AM

Author(s): Aisada A. Uchugonova, Huijing Zhang, Karsten Koenig, Univ. des Saarlandes (Germany)
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Laser-assisted surgery based on multiphoton absorption of NIR light has great potential for high precision surgery at various depths within the cells and tissues. Especially such non-contact method supports contamination-free cell surgery. Here we apply femtosecond laser scanning microscopes for sub-100 nm surgery of human cells and metaphase chromosomes. A mode-locked 85 MHz Ti:Sapphire laser with an M-shaped ultrabroad band spectrum (maxima: 770 nm/830 nm) with an in situ pulse duration at the target of 12 femtoseconds up to 3 picoseconds due to the introduction of chirped mirrors, flint glass wedges, and glass blocks was employed. The results of laser nanoprocessing in cell/chromosome structures have been quantified by atomic force microscopy (AFM) and electron microscopy. These studies demonstrate the potential of extreme ultrashort femtosecond laser pulses at low mean milliwatt powers for sub-100 nm surgery.

Sequential photon absorption induced luminescence from gold nanoparticles

Paper 7903-57 of Conference 7903
Date: Tuesday, 25 January 2011
Time: 8:55 AM – 9:10 AM

Author(s): Adela Ben-Yakar, Nicholas J. Durr, The Univ. of Texas at Austin (United States)
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We will present the properties of multiphoton luminescence (MPL) from gold nanospheres and nanorods. As the excitation pulse duration is changed, we find that unlike band-gap fluorophores, the luminescence does not scale with the inverse of the pulse duration. This result supports the hypothesis that MPL depends on a sequential absorption process. We find a deviation from a strict quadratic dependence of MPL on excitation fluence at long pulse durations. We quantify the effective two-photon action cross sections of various gold nanoparticles and find them to exhibit several orders of magnitude larger cross sections that the brightest quantum dots.

Two-photon autofluorescence spectroscopy of oral mucosa tissue

Paper 7903-58 of Conference 7903
Date: Tuesday, 25 January 2011
Time: 9:10 AM – 9:25 AM

Author(s): Kert Edward, Tuya Shilagard, Suimin Qiu, Vincente Resto, Susan McCammon, Gracie Vargas, The Univ. of Texas Medical Branch (United States)
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Oral carcinoma can often be effectively treated if detected at an early stage of development. Although single photon autofluorescence spectroscopy was been investigated in this regard with some success, two photon spectroscopy has been largely ignored. In this investigation, 2 photon autofluorescence spectroscopy was utilized to detect, monitor and stage DMBA induced carcinogenesis at selected sites in the oral mucosa tissue of hamsters. Subsequent evaluation and grading of the investigated sites by a pathologist revealed a strong correlation between the detected spectroscopic signatures at 780nm, 800nm, 840 nm and 890nm, and the stage of carcinoma in the hamsters.

Single-wavelength STED microscope with multiphoton excitation

Paper 7903-59 of Conference 7903
Date: Tuesday, 25 January 2011
Time: 9:25 AM – 9:40 AM

Author(s): Stephen C. Baer, Massachusetts Institute of Technology (United States)
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I describe an alternative to the expensive form of STED microscope, requiring synchronized pulsed lasers and the cheaper but lower resolution form using CW lasers. The beam of a pulsed laser is split into one beam for multiphoton excitation, and a second beam for quenching, whose pulses are lengthened so their intensity is too low for multiphoton excitation but efficient at quenching. Adjusting path lengths of the beams from the splitter optimizes the timing. This instrument should match resolution performance of the synchronized pulsed laser STED microscope, but particularly when added to an existing multiphoton microscope, should be very inexpensive.

Thresholds for laser-induced DNA damage in nonlinear microscopy

Paper 7903-60 of Conference 7903
Date: Tuesday, 25 January 2011
Time: 9:40 AM – 9:55 AM

Author(s): Oleg Nadiarnykh, Utrecht Univ. (Netherlands); Giju Thomas, Erasmus MC (Netherlands); Johan van Voskuilen, Utrecht Univ. (Netherlands); Henricus J. C. M. Sterenborg, Erasmus MC (Netherlands); Hans C. Gerritsen, Utrecht Univ. (Netherlands)
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Focused femtosecond laser pulses have been shown to cause DNA damage due to three-photon absorption. We quantified DNA damage introduced in ovarian hamster cells in vitro using fluorescent antibodies against cyclobutane-pyrimidin-dimers, where three-photon absorption was confirmed by cubic dependence of fluorescence on excitation power. We further investigated the extent of CPD damage with respect to excitation wavelength between 690 and 820nm, pulsewidth at focal plane varied with custom-built grating pair, and pixel dwell time as compared to more pronounced damage from solar simulator UV source. Damage thresholds are identified for several wavelengths, and relatively safe imaging regimes are suggested.

Femtosecond pump-probe imaging reveals chemical and architectural changes in human melanoma

Paper 7903-61 of Conference 7903
Date: Tuesday, 25 January 2011
Time: 9:55 AM – 10:10 AM

Author(s): Thomas E. Matthews, Ivan Piletic, Maria Angelica Selim, Mary Jane Simpson, Warren S. Warren, Sr., Duke Univ. (United States)
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We have developed a nonlinear imaging method, based on pump-probe spectroscopy in a scanning laser microscope, to directly discriminate and image the two varieties of melanin found in human skin: eumelanin and pheomelanin. We imaged a variety of excised pigmented lesions including benign nevi, compound and dysplastic nevi, malignant melanomas and pigmented basal cell carcinomas. It was found that the melanin in melanomas and carcinomas was predominantly eumelanin, while the surrounding normal tissue and benign lesions were more pheomelanic. We extended this technique to H&E stained slides, allowing co-localization with structural features and making it compatible with traditional pathology samples.

Enhanced-eumelanin fluorescence by stepwise three-photon excitation

Paper 7903-65 of Conference 7903
Date: Tuesday, 25 January 2011
Time: 11:20 AM – 11:35 AM

Author(s): Josef Kerimo, Northeastern Univ. (United States); Milind Rajadhyaksha, Memorial Sloan-Kettering Cancer Ctr. (United States); Charles A. DiMarzio, Northeastern Univ. (United States)
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Eumelanin fluorescence from Sepia officinalis and black human hair was activated with near-infrared radiation and multiphoton excitation. A third order multiphoton absorption by a step-wise process appears to be the underlying mechanism. The activation was caused by a photochemical process since it could not be reproduced by simply heating the samples. The near-infrared irradiation caused photodamage to the eumelanin and could be seen by fluorescence and brightfield imaging and the enhanced emission appeared to originate from the photodamaged region. At least two different components with enhanced fluorescence were activated and could be distinguished by their linear and multiphoton excitation properties.

Multiphoton imaging and quantification of tissue glycation

Paper 7895-9 of Conference 7895
Date: Tuesday, 25 January 2011
Time: 12:00 PM – 12:20 PM

Author(s): Ara Ghazaryan, Jennifer Tseng, Wen Lo, Yang-Fang Chen, Vladimir A. Hovhannisyan, National Taiwan Univ. (Taiwan); Shean-Jen Chen, National Cheng Kung Univ. (Taiwan); Hsin-Yuan Tan, Chang Gung Memorial Hospital (Taiwan); Chen-Yuan Dong, National Taiwan Univ. (Taiwan)
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The present study utilizes the distinct advantages of multi-photon microscopy to improve the reliability of diagnosis. Specifically, the characteristic features of multi-photon autofluorescence (MPAF) and second harmonic generation (SHG) images as well as MPAF spectra of glycated tissues will be presented. In addition, spectral features of glycated tissues will be used to characterize the extent of tissue glycation. Our study shows that multiphoton imaging is capable of providing qualitative and quantitative information of the extent of tissue glycation and that this approach has potential for monitoring AGE formation in the clinical setting.

Simultaneous fluorescence and phosphorescence lifetime imaging

Paper 7903-68 of Conference 7903
Date: Tuesday, 25 January 2011
Time: 1:25 PM – 1:45 PM

Author(s): Wolfgang Becker, Bertram Su, Becker & Hickl GmbH (Germany)
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We present a lifetime imaging technique that simultaneously records fluorescence and phosphorescence lifetime images in laser scanning systems. The technique does not require reduction of the laser pulse repetition rate by a pulse picker and can easily be implemented in standard confocal or multiphoton laser scanning microscopes. Potential applications are oxygen concentration measurements with simultaneous monitoring of cell metabolism, and the migration of nanoparticles of sunscreens and cosmetical products into deep skin layers or inner organs

Integrated en-face optical coherence endomicroscopy and two-photon fluorescence endomicroscopy for simultaneous multimodal imaging

Paper 7889-42 of Conference 7889
Date: Tuesday, 25 January 2011
Time: 1:45 PM – 2:00 PM

Author(s): Jiefeng Xi, Yuying Zhang, Li Huo, Yong-Ping Chen, Xingde Li, The Johns Hopkins Univ. (United States)
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A 1310-nm optical coherence endomicroscopy (OCEM) system and an 800-nm two-photon fluorescence endomicroscopy system were combined into one single configuration. A dichroic mirror was used to make the two wavelength lights share the same path. Both imaging modalities shared the same miniature imaging probe consisting of a DCF, a PZT scanner and a compound lens, suitable for simultaneous acquisition of en face OCEM and TPF images. The core of the DCF delivered 800 nm excitation light for TPF and 1310 nm light for OCEM while the inner cladding of DCF collected the TPF signal. Two-dimensional beam scanning was realized by resonantly scanning a fiber-optic cantilever with a PZT. We obtained en face OCEM images with axial and lateral resolutions of 9.6 ตm in tissue and 1.8 ตm, respectively, co-registered with TPF images with axial and lateral resolutions of 7.6 and 1.4 ตm, respectively. Preliminary results show promising capability of providing simultaneous structural and molecular images.

Femtosecond laser nanofabrication of metal structures through multiphoton photoreduction

Paper 7927-14 of Conference 7927
Date: Tuesday, 25 January 2011
Time: 4:00 PM – 4:20 PM

Author(s): Kevin Vora, SeungYeon Kang, Michael Moebius, Eric D. Mazur, Harvard Univ. (United States)
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We present an ultrafast laser technique for direct-writing gold and silver structures of tunable dimensions. By utilizing nonlinear optical interactions between chemical precursors and femtosecond pulses, we limit metal-ion photoreduction processes to focused spots smaller than that of the diffraction-limit. This creates metal nanostructures in a focal volume that can be rapidly scanned in 3D. By varying the solution chemistry and laser pulse parameters, we demonstrate morphological control of the resulting structures. We fabricate grid and woodpile patterns over hundreds of micrometers in dimensions. We show the process is scalable and possesses optical characteristics suitable for SERS or metamaterial applications.

Using adaptive optics for deep in-vivo multiphoton FLIM

Paper 7903-81 of Conference 7903
Date: Tuesday, 25 January 2011
Time: 5:05 PM – 5:20 PM

Author(s): Simon P. Poland, Gilbert O. Fruhwirth, Tony C. Ng, Simon M. Ameer-Beg, King's College London (United Kingdom)
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Multiphoton microscopy (MPM) combined with Fluorescence lifetime imaging (FLIM) and Fluorescent resonant energy transfer (FRET) provides the ability to image protein-protein interactions in-vivo. Unfortunately as one images more deeply into biological tissue, depth is restricted due to the specimen induced aberrations, which result in deterioration in both the image quality and resolution. Adaptive optics (AO) is a technique which can be used to compensate for these depth induced aberrations. In this paper we will discuss the development a dedicated MPM FLIM-FRET microscope incorporating an AO for use in-vivo applications.

Multiphoton fluorescence lifetime imaging of cleared tissue

Paper 7903-84 of Conference 7903
Date: Tuesday, 25 January 2011
Time: 5:50 PM – 6:05 PM

Author(s): Michael J. Levene, Sam Vesuna, Sonia Parra, Thomas H. Chia, Yale Univ. (United States)
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Optical clearing of fixed tissue enables multiphoton microscopy (MPM) of intrinsic fluorescence to depths of >2 mm in tissue. Large MPM image stacks of BABB cleared tissue offer great opportunity for advancing optical biopsy techniques and 3D histology through the development of 'virtual organs' that are compatible with traditional histological sample preparations, potentially easing its acceptance by the medical community. However, intrinsic sources of fluorescence in tissues often display broad excitation and emission spectra, complicating the ability to achieve molecular contrast. We present MPM-FLIM images of intrinsic fluorescence from mouse organs and human prostate biopsy samples cleared with BABB.

Hybrid MT-OCM imaging platform for in-vivo tissue imaging

Paper 7889-62 of Conference 7889
Date: Wednesday, 26 January 2011
Time: 9:45 AM – 10:00 AM

Author(s): Antti Isomäki, Lars Thrane, Henning E. Larsen, Technical Univ. of Denmark (Denmark); Karsten Koenig, Univ. des Saarlandes (Germany); Peter E. Andersen, Technical Univ. of Denmark (Denmark)
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We report on a combined multiphoton tomography (MT) and optical coherence microscopy (OCM) imaging platform. The combination of the two optical imaging modalities allows for multi-modal cellular and molecular diagnostic imaging. The system is based on a commercial multiphoton tomograph which is modified to accommodate an OCM unit. Two different OCM unit designs are considered here. The first one is using a separate broadband light source at 1.3 micron wavelength range. The second approach takes advantage of sub-12 fs pulses from a Ti:sapphire laser. Ultrafast broadband pulses enable high resolution optical biopsy with simultaneous MT and OCM image acquisition.

Dynamic in-vivo visualization of anastomosis between a prevascularized implantable tissue construct and host circulation

Paper 7897-50 of Conference 7897
Date: Wednesday, 26 January 2011
Time: 11:20 AM – 11:40 AM

Author(s): Sean White, Christopher Hughes, Bernard Choi, Steven C. George M.D., Univ. of California, Irvine (United States)
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The thickness of implantable engineered tissue is restricted by the relatively short diffusion path length of oxygen. One method for overcoming this limitation, termed prevascularization, entails the in vitro formation a vascular network within an engineered tissue construct capable of anastomosing with the host circulation following implantation. We utilized mouse dorsal window chambers to facilitate dynamic imaging of prevascularized tissue implants using laser speckle imaging, multispectral imaging, and multiphoton microscopy. This permits in vivo dynamic visualization and quantification of anastomosis and implant perfusion, and may be used to enhance the design of thick tissue engineered constructs and mechanisms of anastomosis.

ZnSe nanowires as harmonophores for multicontrast nonlinear microscopy

Paper 7946-48 of Conference 7946
Date: Wednesday, 26 January 2011
Time: 5:20 PM – 5:40 PM

Author(s): Richard Cisek, Univ. of Toronto Mississauga (Canada) and Institute for Optical Sciences (Canada); Alex Shik, Harry Ruda, Univ. of Toronto (Canada) and Centre for Advanced Nanotechnology (Canada); Virginijus Barzda, Univ. of Toronto Mississauga (Canada)
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ZnSe nanowires (NWs) can be used as biological labels for harmonic generation microscopy (harmonophores). The orientation dependency between linear polarization of the laser and the NW axis was investigated by recording the second and third harmonic generation as well as multiphoton induced fluorescence images with a nonlinear multicontrast microscope. Imaging individual NWs was achieved with a femtosecond Yb:KGW laser radiating at 1030 nm with 14 MHz pulse repetition rate. The angular dependencies revealed two major factors influencing the aforementioned nonlinearities: (i) the relative dielectric constant between NWs and their environment, and (ii) the surface roughness and bending of the NWs, revealing the latter effect can be dominant.

Nanoprocessing of glass and PMMA by means of near infrared sub-15 femtosecond laser pulses

Paper 7921-19 of Conference 7921
Date: Thursday, 27 January 2011
Time: 11:00 AM – 11:20 AM

Author(s): Huijing Zhang, Karsten König, Maziar Afshar, Dara Feili, Helmut Seidel, Univ. des Saarlandes (Germany)
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A near infrared sub-15 femtosecond laser scanning microscope was employed for structuring of colored glass and PMMA. The 400 mW Ti-Sapphire laser works at 85 MHz with an M-shaped emission spectrum with maxima at 770 nm and 827 nm. By using a high NA objective, light intensity of about 10 TW/cm² at the focal plane can be reached. A mean power of less than 17 mW, which corresponds to the pulse energy of 0.2 nJ, was sufficient for drilling holes and ablating materials. Two-photon fluorescence measurements, which can be performed with the same microscope, reveal the creation of filaments within the specimens, likely caused by self focusing effects. Holes with a diameter of less than 170 nm, were produced without chemical etching. The results are compared with those obtained by using 300 fs and 3 ps laser pulses.

In-vivo third-harmonic generation microscopy at 1550 nm: three-dimensional long-term time-lapse studies in living C. elegans embryos

Paper 7904-50 of Conference 7904
Date: Thursday, 27 January 2011
Time: 11:10 AM – 11:30 AM

Author(s): Rodrigo A. Aviles-Espinosa, Susana I. C. O. Santos, ICFO - Instituto de Ciencias Fotónicas (Spain); Andreas Brodschelm, Wilhelm G. Kaenders, TOPTICA Photonics AG (Germany); Cesar Alonso-Ortega, ICFO - Instituto de Ciencias Fotónicas (Spain); David Artigas-García, ICFO - Instituto de Ciencias Fotónicas (Spain) and Univ. Politècnica de Catalunya (Spain); Pablo Loza-Alvarez, ICFO - Instituto de Ciencias Fotónicas (Spain)
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In-vivo microscopic three-dimensional time-lapse studies (4D) require controlled exposure conditions to preserve sample viability. In this work, we use a 1550nm femtosecond fiber laser to obtain different tissue/structure information of living Caenorhabditis elegans embryos. By exciting Third harmonic generation at 1550nm, the emitted signal is generated at 516nm, enabling the use of standard collection optics and detectors operating near their maximum efficiency. This enables an incident power reduction allowing sample exposure for several hours. Our technique significantly reduces, sample interference (no external markers are required), demonstrating the non-invasiveness and strong potential of this particular wavelength to perform 4D studies.

Multiphoton microscopy and multiplex, multimodal imaging: impact on 21st century healthcare (Keynote Presentation)

Paper 7903-1 of Conference 7903
Date: Sunday, 23 January 2011
Time: 8:15 AM – 8:45 AM

Author(s): Paras N. Prasad, Univ. at Buffalo (United States)
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This talk will present the important roles played by multimodal and multispectral, multiphoton microscopy using CARS, two-photon excitation, second harmonic and sum frequency generation as well as sequential multiphoton absorption. Combining this optical modality of imaging with other medical imaging techniques such as MRI and PET creates a powerful new direction in medical imaging and disease diagnostics by providing a wealth of information, from molecular to morphological, for disease profiling and real time monitoring of therapy. The talk will conclude with a discussion of exciting multidisciplinary opportunities in this field and their impact on 21st century healthcare.

Effective lung cancer medical diagnostics utilizing multiphoton microscopy (Keynote Presentation)

Paper 7903-121 of Conference 7903
Date: Sunday, 23 January 2011
Time: 8:45 AM – 9:05 AM

Author(s): Watt W. Webb, Cornell Univ. (United States)
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Multiphoton microscopy with gold nanoparticles as contrast agents (Keynote Presentation)

Paper 7903-2 of Conference 7903
Date: Sunday, 23 January 2011
Time: 9:05 AM – 9:35 AM

Author(s): Colin J. R. Sheppard, Naveen K. Balla, Singapore MIT Alliance (Singapore) and National Univ. of Singapore (Singapore); Peter T. C. So, Singapore MIT Alliance (Singapore) and Massachusetts Institute of Technology (United States)
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A variety of different nonlinear effects have been shown to occur using gold nanoparticles. Gold nanoparticles are attractive as targeted contrast agents in multiphoton microscopy, because of their low levels of cytotoxicity and resistance to photobleaching. As a result, two photon luminescence (TPL) has become a popular technique in recent years. SHG also occurs with gold nanoparticles. Second harmonic scattering from noble metal nanoparticles is stronger than that from many known nonlinear molecules. Clusters of gold nanoparticles tend to show stronger SHG than single nanoparticles. Since second harmonic scattered light is coherent in nature, careful arrangement of these nanoparticles in a cluster can give rise to strong SHG. Recently, the discrete dipole approximation (DDA) has been extended to predict SHG from small particles of different shapes and under complex illumination conditions. This method makes it possible to look at SHG from a cluster of metal nanoparticles or composite nanoparticles, and offers the possibility to design clusters with desired optical properties.

Examining the feasibility of using multiphoton excited tissue autofluorescence for in vivo human clinical imaging

Paper 7903-18 of Conference 7903
Date: Sunday, 23 January 2011
Time: 3:30 PM – 3:50 PM

Author(s): Johanna M. Dela Cruz, Jesse D. McMullen, Rebecca M. Williams, Warren R. Zipfel, Cornell Univ. (United States)
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Rapid and direct imaging of microscopic tissue morphology, pathology and metabolic state can be achieved using nonlinear imaging of intrinsic tissue fluorophores and second harmonic signals in intact tissue. To design instruments targeted for this type of application, several critical engineering parameters need to be elucidated. Two important questions are what excitation levels and collection efficiencies are required to obtain useable images from different tissue types and whether these levels are mutagenic. Tissue autofluors are weak two-photon fluorophores and very often high laser powers are required for imaging. Here we provide data on the typical average powers required for high signal-to-noise in vivo tissue imaging in several different epithelial tissue types, and access the risk potential of these intensity levels using a mammalian cell gene mutation assay. With 760 nm, 200 fs raster-scanned laser irradiation delivered through a 0.75 NA objective we found negligible mutagenicity at powers less than ~25 mW, while higher laser powers initiated a significant increase in genetic lesions.


Magnetron sputtered filters and mirrors for lasers and multiphoton applications

Paper 7903-118 of Conference 7903
Date: Sunday, 23 January 2011
Time: 4:20 PM – 4:35 PM

Author(s): Michael C. Stanley, Chroma Technology Corp. (United States)
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Structural analysis of articular cartilage using multiphoton microscopy: input for biomechanical modelling

Paper 7903-119 of Conference 7903
Date: Sunday, 23 January 2011
Time: 5:30 PM

Author(s): Magnus B. Lilledahl, Norwegian Univ. of Science and Technology (Norway); David M. Pierce, Gerhard Holzapfel, Technische Univ. Graz (Austria); Catharina de Lange Davies, Univ. of Duissburg-Essen (Germany)
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Cartilage diseases in articular joints is a growing medical problem in the industrialized world, as the population becomes older and the incidence of obesity increases. Biomechanical modeling of cartilage is a valuable tool in the management of cartilage pathologies. We have developed a method for the quantitative characterization of articular cartilage using Fourier image analysis techniques on multiphoton images. Specifically, the primary direction and degree of dispersion of the collagen fibers has been quantified. These parameters can be used directly in a novel constitutive model describing the biomechanical properties of cartilage. As a proof of concept study, we imaged articular cartilage from the knee of chicken, sectioned in three orthogonal planes, to quantify the direction and dispersion of the collagen fibers in three dimensions througout the cartilage volume. A better description of the collagen fibers, yielding a higher fidelity biomechanical model will increase our understanding of the biomechanics of cartilage which will open up new opportunities for improving clinical management of cartilage diseases.

In-vivo multiphoton fluorescence microscopy of epithelial precancer

Paper 7890-17 of Conference 7890
Date: Monday, 24 January 2011
Time: 2:50 PM – 3:10 PM

Author(s): Wei Zheng, Dong Li, Yan Zeng, Jianan Y. Qu, Hong Kong Univ. of Science and Technology (Hong Kong, China)
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In this study, we instrumented a multi-color excitation two-photon fluorescence microscopy system. The 7,12-dimethylbenz(a)anthracene-treated hamster cheek pouch were used as the animal carcinogenesis model and the autofluorescence signals of tryptophan, NADH, collagen and elastin were recorded by a time- and spectral- resolved detection system. The results show that there are obviously differences in the morphology of three-dimensional autofluorescence images between normal, precancerous and cancerous epithelial tissues. The fluorescence lifetime of NADH and tryptophan and the SHG signals from collagen could provide additional approaches to identify cancerous and normal tissues.

In-vivo cellular metabolism of mouse liver revealed by multiphoton microscopy

Paper 7903-62 of Conference 7903
Date: Tuesday, 25 January 2011
Time: 10:35 AM – 10:50 AM

Author(s): Chun-Chin Wang, Wei-Liang Chen, Zhi-Ru Lin, Feng-Chieh Li, Ara Ghazaryan, Hsuan-Shu Lee, Sung-Jan Lin, Chen-Yuan Dong, National Taiwan Univ. (Taiwan)
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We performed a novel method to observe the dynamics of the uptake, processing, and excretion of fluorescent probes in the hepatobiliary system of mice in vivo. A hepatic window was installed on the upper abdomen of mice to acquire time-lapse images. The high resolution images show sequential uptake and processing of fluorescent probes by hepatocytes and the subsequent excretion into bile canaliculi within 50 min. The kinetics of fluorescence intensities in hepatocytes and sinusoids were measured and analyzed in time series and spatial distribution. We demonstrated a promising technique to study intravital hepatic metabolism about normal and diseased mice.

Functional wide-field multiphoton imaging of cellular dynamics by temporal focusing and patterned illumination

Paper 7903-67 of Conference 7903
Date: Tuesday, 25 January 2011
Time: 11:50 AM – 12:05 PM

Author(s): Olivier Dupont-Therrien, Benoit Aube, Stéphane Pagès, Paul De Koninck, Daniel Cote, Univ. Laval (Canada)
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Wide-field temporal focusing is a novel technique to get optical sectioning without the need of a scanning unit. However, spreading the laser beam intensity over large region greatly reduces the photon density and functional imaging of large regions in biological sample has not been shown. We present a microscopy setup that combines beam shaping with temporal focusing of amplified pulses (10 microjoules/pulse) for calcium dynamics imaging in neurons from hippocampus acute slices and cultured cells. Multi-photon video-rate imaging of areas as wide as 8100 microns squared with an optical sectioning under 10 microns at 800nm is achievable with our setup.

Multiphoton lithography and ITO structuring by high repetition-rate sub-15 femtosecond laser pulses

Paper 7920-43 of Conference 7920
Date: Tuesday, 25 January 2011
Time: 6:00 PM

Author(s): Maziar Afshar, Somaie Saremi, Henning Völlm, Dara Feili, Helmut Seidel, Martin H. Straub, Huijing Zhang, Karsten König, Univ. des Saarlandes (Germany)
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We report on experiments using a near-infrared Ti:Sapphire laser system based on a 85 MHz, sub-15 fs resonator. In the negative photoresist SU-8 multiphoton polymerization of 3D structures resulted in a minimum line width of approximately 80 nm at aspect ratios in excess of 100:1. The second part of our contribution deals with sub-wavelength nanostructuring and laser-annealing of thin indium-tin-oxide (ITO) films. The ablation experiments allowed for the generation of cuts of 80 nm in width. For comparison, both our experiments on polymer and ITO were carried out at different pulse widths of up to 2.7 ps. The dependence of cuts on scan parameters as well as ITO film properties such as oxygen content was also investigated.

Holographic spatiotemporal lens (HSTL)

Paper 7925-7 of Conference 7925
Date: Sunday, 23 January 2011
Time: 11:40 AM – 12:00 PM

Author(s): Kouhei Kimura, Satoshi Hasegawa, Yoshio Hayasaki, Utsunomiya Univ. (Japan)
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We propose a holographic spatiotemporal lens (HSTL) to improve spatial resolution of two-photon excitation spot as a new focusing technique of femtosecond laser pulse. Femtosecond laser pulses dispersed by a diffraction grating or a prism-pair are irradiated to a chirped diffractive lens (CSTL) displayed on a spatial light modulator (SLM). The CDL has a spatially chirp of focal length for a design for its corresponding wavelength. The shortest pulse was experimentally obtained only at the focal plane. The pulse duration was also supported with a computer simulation. Furthermore, we demonstrated parallel spatiotemporal focusing using a multiplexed HSTL.

Second-harmonic phase microscopy

Paper 7903-14 of Conference 7903
Date: Sunday, 23 January 2011
Time: 2:10 PM – 2:25 PM

Author(s): Etienne Shaffer, Corinne Moratal, Pierre Marquet, Christian D. Depeursinge, Ecole Polytechnique Fédérale de Lausanne (Switzerland)
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In the past decade, quantitative phase imaging gave a new dimension to optical microscopy, and the recent extension of digital holography techniques to nonlinear microscopy appears very promising, for the phase of nonlinear signal provides additional information, inaccessible to incoherent imaging schemes. We have already reported how the SHG makes possible real-time nanometric 3D-tracking of SHG emitters, such as nanoparticles. In this work, we present the technique and look into its possible applications to biological and life sciences, by presenting some applications of label-free SHG phase microscopy to biological specimens.

Direct laser writing of nonlinear properties in photosensitive glass

Paper 7925-20 of Conference 7925
Date: Monday, 24 January 2011
Time: 9:10 AM – 9:30 AM

Author(s): Gautier Papon, Univ. Bordeaux 1 (France); Jiyeon Choi, CREOL, The College of Optics and Photonics, Univ. of Central Florida (United States); Arnaud Royon, Univ. Bordeaux 1 (France); Martin C. Richardson, Leonid B. Glebov, CREOL, The College of Optics and Photonics, Univ. of Central Florida (United States); Lionel Canioni, Univ. Bordeaux 1 (France)
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A 1030 nm pulsed femtosecond laser has been use to induce modifications in silver containing glass namely femto-photo luminescent glass (FPL) and Photo-thermo refractive glass (PTR). The interaction resulted in the creation of stable silver clusters forming below refraction-limit 3D structures. Those nano-structures exhibit non-linear properties such as SHG and THG as well as fluorescence. Due to multiphoton absorption, free electrons are created enabling the reduction of Ag+ silver ions into Ag0 and subsequently ionized Ag-clusters. The ion concentration gradient creates a buried electric field enabling non-linear properties. Influence of polarization, dose and fluence in the non-linear properties are investigated.

Development of a micromirror-scanned multimodal CARS miniaturized microscope for the in-vivo study of spinal cord disorders

Paper 7903-45 of Conference 7903
Date: Monday, 24 January 2011
Time: 3:53 PM – 4:05 PM

Author(s): Sangeeta Murugkar, Brett Smith, Majid Naji, Univ. of Ottawa (Canada); Craig Brideau, Peter Stys, Univ. of Calgary (Canada); Hanan Anis, Univ. of Ottawa (Canada)
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We discuss the design and implementation of a novel micromirror-scanned multimodal coherent anti-Stokes Raman scattering (CARS) miniaturized microscope probe for imaging of injured and recovering spinal cords in a single living animal over time. The miniaturized microscope design includes fiber based delivery, biaxial scanning using a microelectromechanical system (MEMS) mirror and custom miniaturized optics corrected for chromatic aberration at the pump and Stokes wavelengths for CARS. The basic design concept, major engineering challenges, solutions, and some preliminary results are presented. We demonstrate CARS and two photon excitation fluorescence microscopy in a benchtop setup with the miniaturized optics and MEMS scanning.

Magnetomotive optical coherence microscopy for cell dynamics and biomechanics

Paper 7889-77 of Conference 7889
Date: Wednesday, 26 January 2011
Time: 4:00 PM – 4:15 PM

Author(s): Xing Liang, Benedikt W. Graf, Renu John, Huafeng Ding, Univ. of Illinois at Urbana-Champaign (United States); Hyon-min Song, Purdue Univ. (United States); Gabriel Popescu, Univ. of Illinois at Urbana-Champaign (United States); Alexander Wei, Purdue Univ. (United States); Stephen A. Boppart M.D., Univ. of Illinois at Urbana-Champaign (United States)
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Two methods for high resolution magnetomotive microscopy are presented. These techniques utilize different optical coherence imaging to detect magnetic modulation from nanotransducers. These superparamagnetic nanoparticles can be introduced into biological samples in order to investigate cellular dynamics and biomechanics. Optical coherence microscopy (OCM) and diffraction phase microscopy (DPM) are utilized to detect fixed frequency modulation in phantoms and in live cells. The ability to measure and understand biomechanical properties of cells and their microenvironments, especially for tumor cells, is of great importance and may provide insight for diagnostic and subsequently therapeutic interventions.

Second-harmonic generation and multiphoton microscopy for automatic texture analysis of human of elastic fibers and collagen distribution in human thoracic aorta

Paper 7903-9 of Conference 7903
Date: Sunday, 23 January 2011
Time: 11:50 AM – 12:05 PM

Author(s): Gislaine Vieira, Vitor B. Pelegati, André A. Thomaz, Daniela Peixoto Ferro, Randall L. Adam, Carlos Lenz Cesar, Konradin Metze, Univ. Estadual de Campinas (Brazil)
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A multiphoton optical image guided spectroscopy method for characterization of collagen-based materials modified by glycation

Paper 7902-50 of Conference 7902
Date: Monday, 24 January 2011
Time: 4:10 PM – 4:30 PM

Author(s): Yu Jer Hwang, Joseph Granelli, Julia G. Lyubovitsky, Univ. of California, Riverside (United States)
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In spite of the adverse ageing effects of glycation in vivo, in vitro this process is widely employed to increase stiffness and strength of tissues' and artificial scaffolds'. In-situ optical characterization methods that report on the structures within these materials could clarify the effects of glycation. We employed one-photon fluorescence and multiphoton microscopy method that combined two-photon fluorescence and second harmonic generation signals to characterize collagen hydrogels modified with glyceraldehyde, ribose and glucose. We observed an increase in the in situ fluorescence as well as structural alterations within the materials during the course of glycation.

Course: Biophotonics

Date: Sunday, 23 January 2011
Time: 9:00 AM – 6:00 PM

Instructor(s): Paras N. Prasad, Univ at Buffalo (United States)
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Science and technology breakthroughs in the 21st Century are more likely to occur at the interfaces of disciplines. Biophotonics is defined as the interface of photonics or lightwave technology and the biological sciences. It is a new frontier, offering tremendous prospects for optical diagnostics as well as for light activated therapy, surgery, biosensing and restoration of biological functions. The course will include the following topics: photobiology (interaction of light with cells, interaction of light with tissues, nonlinear optical processes with intense laser beams, photo-induced effects in biological systems), bioimaging (various imaging techniques, fluorescent markers, cellular imaging, imaging of soft and hard tissues, in vivo imaging, dynamic imaging), optical diagnostics (biosensors, fluorescence immunoassay, flow cytometry), optical tweezers and scissors (laser trapping and dissection for biological manipulation, single molecule biophysics studies, DNA-protein interactions), light activated therapy (photodynamic therapy, low level light therapy), nanotechnology (application of nanoprobes, nems), and tissue engineering (use of short pulse lasers for tissue welding, tissue contouring; tissue regeneration).

High-power femtosecond hybrid Ti:sapphire: KrF laser facility and its applications

Paper 7915-12 of Conference 7915
Date: Sunday, 23 January 2011
Time: 2:30 PM – 2:50 PM

Author(s): Andrey A. Ionin, Sergej I. Kudryashov, Alexey O. Levchenko, Leonid V. Seleznev, Dmitry V. Sinitsyn, Nikolay N. Ustinovskii, Vladimir D. Zvorykin, P.N. Lebedev Physical Institute (Russian Federation)
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High-power hybrid femtosecond laser facility consisted of a front-end Ti:Sapphire laser system emitting the third harmonic radiation at the wavelength 248 nm and a set of excimer KrF laser amplifiers is now under development at the Lebedev Institute. Peak power comes up to a few TW right now. Recent experiments on applications of high-intensity femtosecond pulses with wavelengths 248nm and 744 nm for multiphoton and tunnel ionization of different gases, formation of mini-filaments in air under the tight focusing, and laser surface nanostructuring of various solid materials such as titanium, silicon, etc., are discussed.

Delivery and characterization of sub-8fs laser pulses at the imaging plane of a two-photon microscope

Paper 7903-120 of Conference 7903
Date: Sunday, 23 January 2011
Time: 5:30 PM

Author(s): Marcos M. Dantus, Dmitry Pestov, Michigan State Univ. (United States); Bingwei Xu, Haowen Li, Biophotonic Solutions, Inc. (United States)
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We report on a modular and versatile experimental setup that enables straightforward compression (and then shaping) of ultrashort laser pulses at the imaging plane of a two-photon microscope. The system is comprised by commercially available broadband Ti:Sapphire oscillator and 4f shaper. The laser beam is then coupled directly into a high-NA objective. Snapshots of the system dispersion for various objectives are obtained by shaper-assisted scanning of the linear chirp. We use multiphoton intrapulse interference phase scan (MIIPS) to achieve high-finesse pulse compression and verify it via in situ interferometric autocorrelation. We routinely obtain sub-8fs pulse duration at the objective focus.

Breaking stress of glass welded with femtosecond laser pulses at high repetition rates

Paper 7925-24 of Conference 7925
Date: Monday, 24 January 2011
Time: 11:10 AM – 11:30 AM

Author(s): Sören Richter, Sven Döring, Friedrich-Schiller-Univ. Jena (Germany); Thomas Peschel, Ramona Eberhardt, Fraunhofer-Institut für Angewandte Optik und Feinmechanik (Germany); Stefan Nolte, Friedrich-Schiller-Univ. Jena (Germany); Andreas Tünnermann, Friedrich-Schiller-Univ. Jena (Germany) and Fraunhofer-Institut für Angewandte Optik und Feinmechanik (Germany)
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We report measurements of the breaking stress of glass substrates welded with ultrashort laser pulses. The laser pulses at repetition rates in the MHz range are focused at the interface between two substrates, resulting in multiphoton absorption and heat accumulation from successive pulses. The following local melting and subsequent resolidification leads to the formation of bonds at the interface. This results in a very flexible and local bonding process. The breaking stress achievable is discussed in detail in dependence of the laser and material parameters. Also the influence of the induced stress during the writing process will be explained.

Quantitative analysis of collagen fiber orientation in with two-dimensional fast Fourier transform

Paper 7885-62 of Conference 7885
Date: Monday, 24 January 2011
Time: 5:30 PM

Author(s): Wen Lo, National Taiwan Univ. (Taiwan) and National Cheng Kung Univ. (Taiwan); Chiu-Mei Hsueh, Wei-Liang Chen, National Taiwan Univ. (Taiwan); Shean-Jen Chen, National Cheng Kung Univ. (Taiwan); Hsin-Yuan Tan, Chang Gung Memorial Hospital (Taiwan) and Chang Gung Univ. (Taiwan); Chen-Yuan Dong, National Taiwan Univ. (Taiwan)
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The purpose of this study is to investigate the structural features of corneal stroma by second harmonic generation (SHG) microscopy. Since collagen can be induced to generate strong second harmonic generation (SHG) signal, multiphoton excitation provide direct visualization of collagen orientation within corneal stroma. In this work, we collected both forward and backward SHG signals at different depth across the cornea specimens. The SHG images are later analyzed with 2D fast Fourier transform (2D FFT) to obtain the distribution collagen fiber orientations. We found that the aspect ratio obtained from the 2D FFT analysis can be used for the quantitative determination of fiber orientation and that this approach may be used for the diagnosis of pathological corneas.

Multimodality optical imaging of ovarian cancer in a post-menopausal mouse model

Paper 7890-32 of Conference 7890
Date: Tuesday, 25 January 2011
Time: 11:30 AM – 11:50 AM

Author(s): Jennifer M. Watson, Photini F. Rice, David L. Bently, Samuel L. Marion, The Univ. of Arizona (United States); Molly A. Brewer, Univ. of Connecticut Health Ctr. (United States); Patricia B. Hoyer, Jennifer K. Barton, The Univ. of Arizona (United States)
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Our goal is to use optical imaging to detect cancer development on the sub cellular scale. By determining the microscopic changes that precede ovarian cancer we hope to develop a minimally invasive screening test for high risk patients. A mouse ovarian cancer model has been developed by treating mice with 4-Vinylcyclohexene Diepoxide to induce ovarian failure and 7, 12-Dimethylbenz[a]anthracene (DMBA) to induce ovarian cancer. Using optical coherence tomography (OCT) and multiphoton microscopy (MPM) we have obtained co-registered en face images of twenty mouse ovaries ex vivo. Preliminary analysis indicates that OCT and MPM can visualize ovarian microstructure. During the next year we will be completing a long term survival study using post-menopausal mice that have been treated with DMBA to induce cancer and imaged in vivo at time points before and after treatment.

Two-photon phosphorescence lifetime microscopy (2PLM) for high-resolution imaging of oxygen

Paper 7903-79 of Conference 7903
Date: Tuesday, 25 January 2011
Time: 4:35 PM – 4:50 PM

Author(s): Sergei A. Vinogradov, Louise E. Sinks, Emmanuel Roussakis, Univ. of Pennsylvania (United States)
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We present a method for imaging of oxygen in biological tissues, based on the combination of the phosphorescence quenching approach with multiphoton laser scanning microscopy. We address 1) design of two-photon-enhanced oxygen probes whose phosphorescence upon two-photon excitation is enhanced via intramolecular energy transfer from two-photon antennae; 2) modifications to two-photon microscope required for phosphorescence lifetime imaging; 3) interplay between the probe photophysics, spatial and temporal imaging resolution. The functionality of the method was demonstrated in pilot intracellular oxygen imaging experiments and in depth-resolved intravascular and tissue high-resolution oxygen measurements in vivo in the brain.

Controlling ultrafast light with dispersive metamaterials

Paper 7946-29 of Conference 7946
Date: Tuesday, 25 January 2011
Time: 5:00 PM – 5:20 PM

Author(s): Dean P. Brown, UES, Inc. (United States); Augustine M. Urbas, Air Force Research Lab. (United States)
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Because metamaterials possess strong resonances, a strong group delay dispersion (GDD) is also possible, which is an important parameter for ultrafast laser pulses. A metamaterial design was optimized to create a large GDD near a central wavelength of 810nm. Then a multiphoton intrapulse interference phase scan (MIIPS) technique was used to measure the GDD directly over the bandwidth of an ultrafast laser. We found GDD values were an order of magnitude larger than for dispersive optical glass three orders of magnitude thicker. Finally, we explored ways that dispersive metamaterials can shape an ultrafast pulse of light shorter than 20fs.

Two-photon fluorescence vascular imaging with a new fluorene-RGD peptide conjugate

Paper 7910-41 of Conference 7910
Date: Wednesday, 26 January 2011
Time: 8:20 AM – 8:40 AM

Author(s): Kevin D. Belfield, Alma R. Morales, Univ. of Central Florida (United States); Takeo Urakami, Junko Sawada, Sanford-Burnham Medical Research Institute (United States); Ciceron O. Yanez, Univ. of Central Florida (United States); Masanobu Komatsu, Sanford-Burnham Medical Research Institute (United States)
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Multiphoton fluorescence microscopy is a powerful tool in the study of living cells, and features of microvasculature. In the present study, a 2PFM interactive image-analysis method was utilized to evaluate the efficiency of a new 2PA conjugate which was designed to target avß3 integrin. The linear and nonlinear photophysical properties of this RGD peptide fluorescent conjugate were carefully measured. This conjugate was injected into the tail vein of a male C5BL/6 mouse that had been implanted subcutaneously with Lewis Lung Carcinoma cells. The excised tumors consisting of ~ 1 cm3 in volume were whole-mounted and imaged by 2PFM. Ex vivo 2PFM revealed the structure of functional vessels deep within the tumor mass.

Optical data storage in photochromic compounds

Paper 7935-37 of Conference 7935
Date: Wednesday, 26 January 2011
Time: 11:40 AM – 12:00 PM

Author(s): William Dallari, Marco Scotto d'Abbusco, Marco Allione, Elena Samoylova, Francesca Pignatelli, Athanassia Athanassiou, Roberto Cingolani, Alberto Diaspro, Istituto Italiano di Tecnologia (Italy)
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In the present work three dimensional optical data storage in photochromic compounds is demonstrated. Polymers doped with photochromic molecules are used as storage medium. The data are recorded in the media by means of a multiphoton process induced with a pulsed infrared laser coupled to confocal microscopes. The possibility to read and independently erase the data with light of different wavelengths is demonstrated along with the possibility to repeat the write-read-erase cycle on the same material for many times and, despite the system deserves further optimization work, it looks to be a promising tool for 3D optical data storage.

A CARS solution with high temporal resolution

Paper 7903-44 of Conference 7903
Date: Monday, 24 January 2011
Time: 3:41 PM – 3:53 PM

Author(s): Stefanie Landwehr, William Hay, Vishnu Vardhan Krishnamachari, Leica Microsystems CMS GmbH (Germany)
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Confocal and multiphoton microscopy are powerful fluorescence techniques for morphological and dynamics studies of labeled elements. For non-fluorescent components, CARS (Coherent Anti-Stokes Raman Scattering) microscopy can be used for imaging various elements of cells such as lipids, proteins, DNA, etc. This technique is based on the intrinsic vibrational properties of the molecules. Leica Microsystems has combined CARS technology with its TCS SP5 II confocal microscope to provide several advantages for CARS imaging. The Leica TCS CARS combines two technologies in one system: a conventional scanner for maximum resolution and a resonant scanner for highly time resolved imaging. For CARS microscopy, two picosecond near-infrared lasers are tightly overlapped spatially and temporally and sent directly into the confocal system. The conventional scanner can be used for morphological studies and the resonant scanner for following dynamic processes of unstained living cells. The fast scanner has several advantages over other solutions. First, the sectioning is truly confocal and does not suffer from spatial leakage. Second, the high speed (29 images/sec @ 512x512 pixels) provides fast data acquisition at video rates, allowing studies at the sub-cellular level. In summary, CARS microscopy combined with the tandem scanner makes the Leica TCS CARS a powerful tool for multi-modal and three-dimensional imaging of chemical and biological samples. We will present our solution and show results from recent studies with the Leica CARS instrument to illustrate the high flexibility of our system.