Enhanced laser performance in an LD end-pumped YAP/Tm:YAP/YAP bonding rod with concave end faces

We demonstrate the effects of thermal bonding and concave end faces on the laser performance of 795 nm LD end-pumped Tm:YAP crystals for the first time. Analysis of the thermal focal length shows that the thermal lensing effect can be effectively compensated by the concave end faces. By combining the thermal bonding with the concave end faces, a maximum output power of 42.5 W is achieved on the concave YAP/Tm:YAP/YAP bonding rod with a negative curvature radius of 500 mm, corresponding to a slope efficiency of 47.4% and an optical-optical (O-O) conversion efficiency of 41.6%. Moreover, the beam quality factors Mx2/My2 are fitted to 1.67/1.69. Compared with the flat YAP/Tm:YAP/YAP bonding rod, the concave YAP/Tm:YAP/YAP bonding rod significantly increases the maximum output power from 36.56 W to 42.5 W, with an approximately 4% improvement in both the slope efficiency and O-O conversion efficiency. These results indicate that the combination of thermal bonding and concave end faces can effectively improve the heat dissipation capacity and mitigate the thermal lensing effect, thereby yielding near-infrared (NIR) laser output with high performance.