Description of the Ytterbium-doped Potassium-Gadolinium Tungstate Crystal
Yb3+: KGd(WO4)2 (Yb: KGW) is a laser-active material. The Yb: KGW crystal is anticipated to replace the Nd:YAG and Yb:YAG crystals in a diode-pumped high-power laser system. It may be applied in femtosecond lasers with high power and short pulse duration, and in other applications.
Advantages of Yb: KGW
- The absorption line width is broad, and the pump wavelength of the LD pump source with phase adjustment can be attained without strict temperature control;
- The quantum defect is low, and the pump wavelength is very near the laser output wavelength, thereby resulting in a high intrinsic laser slope efficiency; the quantum efficiency is theoretically up to 90%;
- Since the pumped energy level is near the upper laser level, the thermal load is reduced due to the absence of radiative relaxation, being approximately one-third that of similar Neodymium-doped laser materials;
- There is no excited-state absorption and no upconversion, so the optical conversion efficiency is high;
- The fluorescence lifetime is more than three times that of Neodymium-doped laser materials, which benefits energy storage;
Specifications of the Ytterbium-doped Potassium-Gadolinium Tungstate Crystal
Material Specifications
|
Chemical Formula
|
Potassium-Gadolinium Tungstate
|
Crystal Structure
|
monoclinic double tungstate
|
Density
|
7.27 g/cm³
|
Transmission Range
|
0.35–5.5 µm
|
Mohs Hardness
|
4 to 5
|
Refractive Indices at 1060 nm
|
ng = 2.037, np = 1.986, nm = 2.033
|
Optical and Thermal Properties
|
Thermal Conductivity
|
Ka = 2.6 W/mK, Kb = 3.8 W/mK, Kc = 3.4 W/mK
|
Thermo-optic Coefficient @1064 nm
|
dnp/dT = -15.7 × 10⁻⁶ K⁻¹
|
dnm/dT = -11.8 × 10⁻⁶ K⁻¹
|
dng/dT = -17.3 × 10⁻⁶ K⁻¹
|
Thermal Expansion
|
αa = 4×10⁻⁶ /°C
|
αb = 3.6×10⁻⁶ /°C
|
αc = 8.5×10⁻⁶ /°C
|
Melting Temperature
|
1075 °C
|
Absorption Cross-Section
|
1.2×10⁻¹⁹ cm²
|
Stimulated Emission Cross-Section (E||a)
|
2.6×10⁻²⁰ cm²
|
Laser Wavelength
|
1023–1060 nm
|
Laser Threshold
|
35 mW
|
Energy of the Stark Levels (in cm⁻¹) of the 2F5/2 Manifolds of Yb3+ at 77 K
|
10 682, 10 471, 10 188
|
Energy of the Stark Levels (in cm⁻¹) of the 2F7/2 Manifolds of Yb3+ at 77 K
|
535, 385, 163, 0
|
Optical Damage Threshold, GW/cm²
|
20
|
Applications of the Ytterbium-doped Potassium-Gadolinium Tungstate Crystal
- Nonlinear Microscopy
- Oscillators
- Regenerative Amplifiers