Thermal effects and their mitigation in end-pumped solid-state lasers

Degradation in beam quality due to aberrated thermal lensing and depolarization loss due to stress induced birefringence in end-pumped edge-cooled solid-state lasers are investigated. A simple model for the dependence of thermal lensing and degradation in beam quality on the transverse intensity profile of the pump beam is presented. Experimental measurements of thermal lensing, degradation in beam quality and depolarization loss in a diode-bar-end-pumped Nd:YAG rod support the main predictions of the model and, in addition, show that there can be significant extra heating under non-lasing conditions compared to lasing conditions. The role of energy transfer upconversion as a mechanism for additional heat loading under non-lasing conditions is considered. Finally, various strategies for limiting the impact of thermal lensing and thermally induced birefringence on laser performance in simple end-pumped cavity configurations are reviewed.