Diffraction losses of high power solid state lasers

A uniform pumping distribution is very important in a side pumped rod geometry. Based on space-dependent rate equations, the threshold pump power and the TEM 00 mode output power of a solid state laser with a uniform pump are obtained. The diffraction losses arising from thermally induced spherical aberration have been estimated by the Strehl intensity ratio. The diffraction losses may prevent the solid state laser from ultrahigh power levels before the thermal fracture limitation. The diffraction losses for different sizes of laser beams and the laser rods are discussed. A significant increase in average power and a great decrease in thermal distortion and birefringence at cryogenic temperature have been analyzed in cooperation with thermal induced diffraction losses.