Q-switch regime of 3-μm Er:YAG lasers

A mathematical model, based exclusively on spectroscopic data concerning radiative, nonradiative, and energy transfer processes, is proposed and used to simulate the Q-switch regime of a 3-mu m Er:YAG laser, The connection between the main energy transfer mechanisms that make possible generation on the self-saturated transition I-4(11/2) --> I-4(13/2) (upconversion from I-4(13/2) and I-4(11/2) and cross relaxation from S-4(3/2)) and the giant pulse characteristics are discussed. The radiative as well as nonradiative losses during optical pumping and giant pulse generation are defined and evaluated. A particular attention is given to the frustrated total internal reflection (FTIR) Q-switch which demonstrated real qualities for 3-mu m erbium lasers. The reasons responsible for experimental performances of Q-switched Er:YAG lasers inferior to those predicted by the mathematical modeling are analyzed.