Yb: YAG
( Ytterbium Doped Yttrium Aluminum Garnet)
Yb:YAG crystal is an excellent laser-active materials and more suitable for DPSS
(diode-pumping solid state ) lasers than the traditional Nd-doped systems. It
can use be pumped 0.94μm and 0.97μm laser diodes for pumping which are much
cheaper than 0.81um diodes and can get higher quantum efficience. Yb:YAG crystal
has also a much larger absorption bandwidth to reduces thermal management
requirements for diode lasers, a longer upper-state lifetime, three to four
times lower thermal loading per unit pump power compared with the commonly used
Nd: YAG crystal. Yb:YAG crystal (1030nm)
is expected to replace Nd:YAG crystal (1064nm)
for high power DPSS lasers and
its second harmonic ( 515nm )
may replace large volume Ar-ion lasers ( 514nm).
1. Main
Advantages of Yb:YAG Crystals
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 and large mechanical strength
-
High optical quality
2. Optical and
Spectral Properties of Yb:YAG Crystals
|
Laser Transition |
2F5/2→2F7/2 |
|
Laser Wavelength |
1030nm |
|
Photon Energy (J) |
1.93*10-19 @1030nm |
|
Emission Linewidth (nm) |
9 |
|
Emission Cross Section (cm2) |
2.0*10-20 |
|
Fluorescence Lifetime (ms) |
1.2 |
|
Diode Pump Band (nm) |
940or 970 |
|
Pump Absorption Band Width (nm) |
8 |
|
Index of Refraction |
1.82 |
|
Thermal Optical Coefficient (/K) |
9*10-6 |
|
Loss Coefficient (cm-1) |
0.003 |
3. Properties of Yb:YAG (Physical and chemical)
|
Crystal Structure |
Cubic |
|
Lattice Parameters (nm) |
1.201 |
|
Melting Point (K) |
2243 |
|
Moh Hardness |
8.5 |
|
Density (g/cm3) |
4.56+/-0.04 |
|
Specific Heat (0-20) (J/g.cm3) |
0.59 |
|
Modulus of Elasticity (GPa) |
310 |
|
Young's Modulus (Kg/mm2) |
3.17*104 |
|
Poisson Ratio (est.) |
0.3 |
|
Tensile Strength (GPa) |
0.13~0.26 |
|
Thermal Expansion Coefficient
(/K) (0~250℃) |
[100]Direction:8.2*10-6 |
|
[110]Direction:7.7*10-6 |
|
[111]Direction:7.8*10-6 |
|
Thermal Conductivity (W/m/K) |
14(@20℃ |
|
10.5(@100℃ |
|
Thermal Optical Coefficient (dn/dT, /K ) |
7.3*10-6 |
|
Thermal Shock Resistance(W/m) |
790 |
|
Solubility |
Water: Insoluble;
Common Acids: Slightly |
4. Standard Products specification
|
Dopant concentration |
Yb:0.5～25
at% |
|
Orientation |
[100]or[111]within 5o
|
|
Wavefront Distortion |
≤ 0.125λ/inch |
|
Extinction Ratio |
≥28 dB |
|
Rod Sizes |
Diameter:2～20mm,Length:5～150mm
Upon request of customer |
|
Dimensional Tolerances |
Diameter:+0.00"/-0.002"mm,
Length: +/-
0.02" |
|
Barrel Finish |
Ground Finish: 400# Grit |
|
Parallelism |
≤10" |
|
Perpendicularity |
≤5′ |
|
Flatness |
λ/10 |
|
Surface Quality |
10-5(MIL-O-13830A) |
|
Chamfer |
0.006"+/-0.002" at 45o+/-5o
|
|
AR Coating Reflectivity |
≤ 0.25% (@1030nm) |
|
Single pass loss |
<3*103cm-1 |
5. Typical
size Of Yb.:YAG laser crystal
1.
Yb:YAG,
5%, 8%
and 10% Yb,
Ø 3 mm x 3 mm,
AR
coating on both sides: 940 and 1030 nm
2.
Yb:YAG disk, 10
% Yb
Ø10.0
mm +/- 0.3 mm x 0.25 mm +0.1/- 0.05 mm flat/flat
Surface quality S/D: 10/5
flatness lambda/8 - lambda/10 at 632.8 nm
parallism of endfaces better 10 of arc second.
Coating: 1 side: HT 940 nm
2.side:HR 1030 nm
|
