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Introduction
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 is expected
to replace Nd:YAG crystal for high power diode-pumped lasers
and other potential applications.
 Very low fractional heating, less than 11%
Very high slope efficiency
Broad absorption bands, about 8nm@940nm
No excited-state absorption or up-conversion
Conveniently pumped by reliable InGaAs diodes
at 940nm(or 970nm) High thermal conductivity
High optical quality
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Basic Properties:
| Crystal Structure |
Cubic |
| Lattice Parameters |
12.01 Å |
| Melting Point |
1970 °C |
| Moh Hardness |
8.5 |
| Density |
4.56±0.04g/cm 3 |
| Specific Heat (0-20) |
0.59J/g.cm 3 |
| Modulus of Elasticity |
310GPa |
| Young's Modulus |
3.17X10 4 Kg/mm 2 |
| Poisson Ratio |
0.3(est.) |
| Tensile Strength |
0.13~0.26GPa |
| 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 |
The
Sellmeier equations (°C in µm for YAG):
n ^2 = 2.08745 + 1.2081 °C ^2 /(°C^ 2 - 0.02119 )+ 17.2049
°C ^2 /(°C ^2 - 1404.45 )
Optical and
Spectral Properties
| Dopant concentration |
Yb: 0.5 ~ 25 at% |
| Laser Transition |
2 F 5/2 °C 2 F 7/2 |
| Laser Wavelength |
1030nm |
| Photon Energy |
1.93×10-19J(@1030nm) |
| Emission Linewidth |
9nm |
| Emission Cross Section |
2.0×10-20cm 2 |
| Fluorescence Lifetime |
1.2 ms |
| Diode Pump Band |
940nm or 970nm |
| Pump Absorption Band Width |
8 nm |
| Index of Refraction |
1.82 |
| Thermal Optical Coefficient |
9 × 10-6/ °C |
| Loss Coefficient |
0.003 cm -1 |
Yb:YAG's Specifications:
| Orientation: |
<111> or <100]> crystalline
within 5° |
| Wavefront distortion : |
l /8 per inch @ 633 nm |
| Extinction Ratio: |
>25dB |
| Dimension Tolerances |
Rods with diameter: ±0.025 mm ,
Length: ±0.5 mm |
| Surface quality: |
10/5 Scratch / Dig per MIL-O-1380A
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| Parallelism: |
< 10 arc seconds |
| Perpendicularity: |
< 5 arc minutes |
| Flatness: |
< l /10 @ 633 nm |
| chamfer: |
<0.1 mm @ 45deg. |
| Barrel Finish: |
50-80 micro-inch (RMS) , |
| AR Coating Reflectivity |
= 0.25% |
Note: The other specification and dimension is available
too |
Laser Crystals