Tm: YVO4 crystal, as a promising solid-state laser working material, has many remarkable characteristics.
- Suitable for AlGaAs laser diode pumping (3H6-3H4, transition wavelength about 800 nm)
- High efficiency near infrared laser output due to cross relaxation between ions.
- Broad tunability around 2000 nm.
- In comparison with T：m YAG, Tm: YVO4 has larger laser emission cross section thanks to its strong phonon coupling behavior.
- The 1.9 μm laser of Tm:YVO4 crystal is eye-safe and has high transparency in the atmosphere. Therefore, Tm:YVO4 crystals can be used in infrared radar and long-distance infrared sensors, and also have important applications in laser medicine.
Photonchina can provide Tm:YVO4 crystals with different doping concentrations according to customer needs, and already has the capacity for mass production.
The basic properties of the crystal are shown in the table below.
Photonchina Tm:YVO4 Properties
|Crystal Structure||Tetragonal, D4h -l41/amd|
|Mohs Hardness||5 glass-like|
|Thermal expansion Coefficient(300K)||aa=4.43*10-6 /K, ac=11.37*10-6 /K|
|Thermal optical coefficient(300K)||dno /dT=8.5×10-6 /K; dne /dT=2.9×10-6 /K|
|Thermal Conductivity Coefficient(300K)||||C: 5.23 w/m/k; ⊥C:5.10w/m/k|
|Emission linewidth(5% Tm)||64nm|
|Emission cross section(5% Tm)||2.7 x10-20 cm2 @1.9um|
|Fluorescence lifetime(4.8% Yb)||0.8ms|
Spectroscopic properties of Tm:YVO4 crystals
After measuring sigma and pi polarized absorption spectra of Tm:YVO4 crystal at room temperature, researcher calculate the intensity parameters of Tm3+ in crystal YVO4 which are omega 2 = 1.9416 x 10(-20) (cm2), omega 4 = 0.1568 x 10(-20) (cm2), omega 6 = 0.3963 x 10(-20) (cm2) by Judd-Ofelt theory. The spectra characteristic parameters, such as radiative transition rates, luminescence branching ratio, total radiative lifetime and integral cross-section are also included.
It is shown that the spontaneous rate of the transition 1D2–>3F4 is much higher than that of the transition 1D2 to other levels.
The order of magnitude of the cross relaxation probability between active ions and sensitive ions in Tb,Tm∶YVO 4 crystal and the cross relaxation among active ions in Tm∶YVO 4 are close with that of the non radiating transition probability and the radiant transition probability of higher level to lower level. The formula to estimate the laser threshold in the crystal including two sort codoped ions must take into account the cross relaxation among the ions.
Some researchers have found that doping Tb 3+ ions in Tm∶YVO 4 increases intensity of lasing light and minifies the laser threshold at 1.9 μm wavelength.