Pedagogically fast model to evaluate and optimize passively Q-switched Nd-doped solid-state lasers

The coupled rate equations with the spatial overlap effect for four-level passively Q-switched lasers are fully considered. A transcendental equation is derived for the residual fraction of the inversion density after the finish of the Q-switched pulse. Comprehensive calculations for the transcendental equation were executed to attain an analytical function for precisely fitting the residual fraction of the inversion density. With the fitting function, a pedagogical model with the correction for high output coupling is developed to straightforwardly analyze the output pulse energy and peak power. Detailed experiments are carried out to validate the model. (C) 2021 Optical Society of America

Automated summary

The study fully considers the coupled rate equations with the spatial overlap effect for four-level passively Q-switched lasers, and derives a transcendental equation for the residual fraction of the inversion density. Comprehensive calculations are done to attain an analytical function for fitting the residual fraction. A pedagogical model with correction for high output coupling is developed for straightforward analysis of output pulse energy and peak power, validated through detailed experiments.