Circular output from a high power Nd:YLF slab laser

Neodymium-doped Yttrium Lithium Fluoride (YLF) lasers have traditionally been power-limited by the relatively low tensile strength of the crystal. When power-scaling solid-state lasers, the choice of the gain media geometry, the doping level, and the pumping scheme is dictated by minimizing the impact of thermally induced stress. To date the slab architecture has been the most successful for scaling the average-power of Nd:YLF lasers due to its favorable thermal management. However, for efficient high-radiance laser action it is also necessary to have a good overlap between the cavity mode and the planar gain volume. We present the performance characteristics for an end-pumped slab-laser utilizing a stable low-loss resonator configuration that transforms a circular cavity mode at the output coupler into a very high aspect ratio elliptical beam in the slab gain element to match the pumped volume. The optical arrangement for transforming the beam shape is also suitable for a double-pass slab amplifier configuration. A polarized CW output power of 50W, on the weaker Nd:YLF 1053nm transition was obtained with a single slab gain element and 110W of incident pump power from three spatially multiplexed diode bars. Laser threshold was around 7W and the slope efficiency, with respect to incident power, 46%