Femtosecond Laser Mavericks is based on Chromium-activated Forsterite Single Crystals

Chromium-Doped Forsterite Crystal (Cr:Mg2SiO4) - PX

Chromium-activated Forsterite Single Crystals, Mg2SiO4:Cr4+,
are excellent tunable laser crystals for both pulsed and CW lasers.

Crystal structure

Rhombic

Lattice parameter

a=4.77Å, b=10.28Å, c=6.00Å

Refraction indices

nz=1.670, ny=1.651, nx=1.635

Density

3.217 g/cm3

Hardness

7 mohs

Axial Characteristic

Biaxial

Melting point

1895C

Crystal Size (boule)

Diameter 30 x 140 mm

Damage threshold

200 MW/cm2

Saturation energy density

2J/cm2

Absorption cross section

1.88 x 1018 cm2

Thermal expansion coefficient

9.5 x 10-6

Thermal conductivity

0.08 (300 W/cmK)

Relaxation time of terminal lasing level

<10ps

Stimulated emission cross section

1.44 x 10-19/cm2

Spontaneous fluorescence

2.7 x 10-6s

Loss coefficient on wavelength 1230nm

0.005 - 0.03 / cm

Absorption coefficient on wavelength 1064nm

0.7 - 2.5 / cm

Fluorescence band

680 - 1400 nm

Tuning range

1130 - 1348 nm

Lasing wavelength (centre)

1235nm (pulsed)

 

1244nm (CW)

Room-temperature fluorescence lifetime

Appr. 2.7 x 10-8s

Gain cross section

Appr. 1.45 x 10-19 cm2

Dopant concentration range

0.05-0.6%

End face flatness

l/10 wave across 80% of aperture

Surface roughness

l/10

Perpendicularity

within 5 arc minutes

Parallelism

30 arc seconds or less

Scratch-dig

10-10

 

 

Cr:Forsterite crystal is a new tunable laser material that fills the spectral vacancy in the near-IR region. The tuning range covers the important spectral range from 1167 nm to 1345 nm, which provides a minimal dispersion in optical fibers. The Cr:Forsterite laser eventually explores its niche applications for semiconductor characterization, eye-safe ranging, medical , industrial and scientific research. Both pulsed and continuous-wave (CW) laser operation have been obtained when pumped with 532, 578, 629 and 1064 nm.

Physical, Thermal and Optical Properties - CX

Chemical Formula Cr:Mg2SiO4
Concentration ~3 - 6 x1018 cm-3
Melting Point 1890 ºC
Density 3.22 g/cm3
Mohs Hardness 7
Thermal Expansion Coefficient 9.5x10-6
Thermal Conductivity 8 W /m /K (300 K)
Stimulated Emission Cross Section 1.44x10-19 cm-2
Relaxation Time of Terminal Lasing Level <10 ps
Radiative Lifetime 25 ms
Spontaneous Fluorescence 2.7 ms
Loss Coefficient 0.02 cm-1
Refractive Index 1.635

Spectroscopic and Laser Properties

Major Pumping Bands 850-1200, 600-850, 350-550 nm
Fluorescence Band 680-1400 nm
Room-temperature Fluorescence Lifetime ~ 3 ms
Lasing Wavelength (center) 1235nm (pulsed), 1244 nm (CW)
Spectral Bandwidth 30 nm (pulsed), 12 nm (CW)
Typical Slope Efficiency 23% (pulsed), 38% (CW)
Tuning range 1167 - 1345 nm
Gain Cross Section ~1.45x10-19 cm2

 

Del Mar Photonics