Thermal effects of the zig-zag Yb:YAG slab laser with composite crystals

A new slab configuration is designed based on the traditional Yb:YAG Total-Reflection Active-Mirror (TRAM) slab laser. The grad-doping method is proposed to improve the pump uniformity of the gain medium. A thermal analysis model is established by the ray-tracing software and finite element method. The thermal effects of the uniform doping medium and gradient doping medium are investigated according to the model, respectively. It shows that the maximum temperature and stress decrease obviously by the grad-doping method. A method based on ray-tracing is proposed to evaluate the thermal lensing effect and spherical aberration effect, and it is also suitable for other gain mediums with complex structures. The results indicate that the gain medium has less thermal effect and better beam quality by the grad-doping method. The TRAM slab with gradient doping concentration is also a promising configuration to obtain higher power output.