Highly efficient quasi-cw Nd:YAG laser side-pumped in a diffusive cavity by P-polarized stacked diode beams

We have demonstrated a highly efficient quasi-cw Nd:YAG laser with a novel side-pumping configuration using micro-lens free stacked-diode-bars. In this configuration, the fast-axis of the diode bars is arranged in parallel to the rod axis which means highly efficient P-polarization pumping of the Nd:YAG rod. The pumping beams are coupled into a cylindrical diffusive reflector by using wedge lenses (1-dimensional lens duct). The pump radiation in the slow axis direction is focused by the cylindrical surface of the wedge lens, and the radiation in the fast axis direction is transferred by the total internal reflection. Six micro-lens free diode bars are arranged around the Nd:YAG rod. The transfer efficiency of the wedge lens was 89%. Laser power of 270 W was obtained at the beam quality of 20 mm mrad at the electric efficiency of 18.4%. The experimental results are well explained by calculations and we consider further enhancement of the efficiency is possible by optimizing the diffusive cavity design.