Transverse modes and beam spatial quality in microchip lasers

Abstract

We analyze the transverse modes in flat-flat mirror microchip-laser resonators, which occur due to the gain guiding and the thermal lensing. We rigorously calculate the transverse-mode functions, their eigenfrequencies, and their generation-threshold conditions. We apply a plausible assumption that the mode amplitudes in multi-transverse-mode emission are proportional to the individual gain factors of each mode, and we estimate the beam quality factor for the multi-transverse-mode emission. This simple and intuitive approach leads to the beam quality estimations corresponding well to the experimental measurements performed here.

Postprint (published version)