Accurate thermal stress induced birefringence measurement of laser crystal with cavity ring-down technique

One of the main sources of beam quality deterioration encountered in high-power diode-pumped solid-state lasers is the thermal stress induced birefringence. Cavity ring-down (CRD) technique is applied to the accurate measurement of thermal stress induced birefringence of laser crystal under pump diode laser illumination. Measurements of the pump laser illumination induced temperature profile and thermal stress induced birefringence retardance distribution in the laser crystal are performed and compared to numerical calculations to determine the absorption and thermal diffusivity of the laser crystal and further the relevant stress-optical constant. The experimental results demonstrated that CRD is a highly sensitive and accurate technique to measure the thermal stress induced birefringence and relevant stress-optical constant of laser crystals, which is helpful for the evaluation and optimization of the performance of high-power laser systems.