Optical tuning of vertical-cavity surface-emitting laser side-pumped neodymium-doped yttrium aluminum garnet laser cavity

Abstract High-power 808 nm vertical-cavity surface-emitting laser (VCSEL) chips have unique characteristics for neodymium-doped yttrium aluminum garnet (Nd:YAG) laser pumping compared with conventional edge-emitting laser bars, including a chip surface with high reflectivity, near flat top distribution in the near field, larger emitting width and smaller divergence. A novel symmetrical pump cavity with an inter-reflective chamber was invented by introducing even-numbered pumping geometry and removing the conventional internal reflector. Several optical tuning measures were taken to improve the uniformity of the pumping distribution, including power and spectrum balancing in the cross-section and the long axis of the laser rod, a diffuse mechanism in the pump chamber by a frosted flow tube and optional eccentric pumping geometry. A series of VCSEL pumping experiments were conducted and optical tuning measures were evaluated through distribution profiles and efficiencies. A new design philosophy for the VCSEL side-pumped Nd:YAG laser cavity was finally developed.