Efficient laser with a rectangular active element

A solid-state laser with a rectangular active element was constructed. When this element was a neodymium-activated gadolinium gallium garnet crystal and the laser was operated under conditions ensuring a high average power, the output power was 180 W at a pulse repetition frequency of 25 Hz and the absolute efficiency was ~ 3%. The divergence of the output radiation did not exceed 10 mrad and the specific output power was 7.5 W/cm³.