Thermal lensing and laser performance of Tm:LuAG crystal at room temperature

In this paper, thermal effect of a diode-end-pumping Tm:LuAG crystal is analyzed and the lasing characteristics at room temperature are also investigated. Based on a thermal model, the thermal focal length of Tm:LuAG crystal is calculated at different pump energies between 50 mJ and 300 mJ. The sensitivity factor of the thermal lens M=d(1/f)/dP_abs is estimated to be 0.36 m^-1/W or 36 m^-1/J. The thermal focal length of Tm:LuAG crystal is also measured at different pump energies. Results show that the experimental data are very well in accordance with the theoretical calculations. Laser characteristics of Tm:LuAG crystal at room temperature are also investigated. Under a pump energy of 300 mJ, the maximum output energy of 41.0 mJ is obtained, with a slope efficiency of 20.8%. The build-up time of the pulse is 2.76 ms, and the beam quality factor is measured to be M ²=1.17.