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-/spl mu/m Er:YAG laser. The connection between the main energy transfer mechanisms that make possible generation on the self-saturated transition /sup 4/I/sub 11/2//spl rarr//sup 4/I/sub 13/2/ (upconversion from /sup 4/I/sub 13/2/ and /sup 4/I/sub 11/2/ and cross relaxation from /sup 4/S/sub 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-/spl 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.