Yb:YAG (Ytterbium Doped Yttrium Aluminum Garnet)
Yb:YAG is one of the most promising laser-active materials
and more suitable for diode-pumping than the traditional Nd-doped systems.
Compared with the commonly used Nd:YAG crsytal , Yb:YAG crystal has a much
larger absorption bandwidth to reduce thermal management requirements for
diode lasers, a longer upper-laser level lifetime, three to four times lower
thermal loading per unit pump power. Yb:YAG crystal has the potential to
replace Nd:YAG crystal for high power diode-pumped lasers.
Newlight Yb:YAG features
Low fractional
heating, less than 11%
High slope efficiency
Broad absorption bands, about 8nm@940nm
No excited-state absorption or
up-conversion
Can be conveniently pumped by
reliable InGaAs diodes at 940nm(or 970nm)
High thermal conductivity
High optical quality
Basic Properties:
Crystal Structure |
Cubic |
Lattice Parameters |
12.01 Å |
Melting Point |
1970
°C |
Moh Hardness |
8.5
|
Density |
4.56
g/cm3 |
Specific Heat |
0.59
J/g.cm3 |
Modulus of Elasticity |
310
GPa |
Young's Modulus |
3.17X104 Kg/mm2
|
Poisson Ratio |
0.3
(est.) |
Tensile Strength |
0.13~0.26 GPa |
Thermal Expansion Coefficient |
[100]Direction:8.2x10-6/°C (0~250°C )
|
[110]Direction:7.7x10-6/°C (0~250°C )
|
[111]Direction:7.8x10-6/°C (0~250°C )
|
Thermal Conductivity |
14W/m/K(@20 °C ) |
10.5W/m/K(@100 °C ) |
Thermal Optical Coefficient (dn/dT) |
7.3×10-6/°C |
Thermal Shock Resistance |
790W/m |
Optical and Spectral Properties
Dopant concentration |
Yb:
0.5 ~ 25 at% |
Laser
Transition |
2F5/2
- 2F7/2 |
Laser
Wavelength |
1030nm |
Photon Energy |
1.93×10-19J (@1030nm) |
Emission Linewidth |
9 nm
|
Emission Cross Section |
2.0×10-20cm2
|
Fluorescence Lifetime |
1.2
μs |
Diode
Pump Band |
940nm
or 970nm |
Pump
Absorption Bandwidth |
8 nm
|
Index
of Refraction |
1.82
|
Sellmeier
equation
( λ in
μm) |
n2=2.08745+1.2081
λ2/(λ2-0.02119
)+17.2049 λ2/(λ2-1404.45) |
Thermo-Optical Coefficient |
9×10-6/ °C |
Loss
Coefficient |
0.003
cm-1 |
Specifications of finished Yb:YAG crystals
Orientation:
|
axis along
<111> or <100> direction |
Wavefront Distortion:
|
λ/8
per 25mm @ 633 nm |
Extinction Ratio:
|
> 25dB |
Dimension Tolerances
|
rods
with diameter: ±0.025 mm , Length: ±0.5 mm |
Surface Quality:
|
10/5 Scratch/Dig MIL-O-1380A
|
Parallelism:
|
<10 arc seconds
|
Perpendicularity:
|
<5 arc minutes
|
Clear Aperture:
|
>90% |
Surface Flatness: |
<
λ/10
@ 633 nm |
Chamfer:
|
<0.1 mm @ 45o |
AR Coating Reflectivity |
R < 0.25% |
|