Calculation of thermo-optical effects in Nd:YAG rod

Thermal lens and stress induced birefringence are two key effects that must be considered in the design and optimization of high-power DPL. This paper discusses the general way of calculating the thermal lens by finite-difference beam propagation method and that of calculating the stress induced birefringence using the elasto-optical coefficients of the material. The effects of the thermal lens and the stress induced birefringence on beams were calculated for a 6 cm Nd:YAG rod. The results show that the wavefront amplitude in the center of the rod increases about 6% after one pass, and the wavefront phase difference between the center and the edge of the rod reaches nearly 20 wavelengths; meanwhile, about 30% power losses due to birefringence．