The temperature distribution and thermomechanical strains in passively Q-switched YAG:Nd3+/YAG:Cr4+ and GGG:Nd3+/GGG:Cr4+ microchip lasers

The heat processes in microchip Nd³⁺:YAG- and Nd³⁺:GGG-lasers passively Q-switched by Cr⁴⁺:YAG and Cr⁴⁺:GGG absorbers are considered. The specific heat power is determined from the system of rate equations described the processes of generation/absorption of laser radiation and generation of heat both in the generation medium and the absorber. At known time dependences and space distributions of the specific heat power the distributions of the temperature in both lasers are determined from the heat conduction equation. Based on the distributions of the temperature, the thermo-mechanical strains are estimated. It is shown that maximal values of the thermomechanical strains in GGG-based laser are in ~1.5 times higher than in YAG-based one. Even at the significant heat power the maximal values of the thermo-mechanical strains for both crystals are 4-6 times lower than their limiting values.