Condensation of the stimulated emission spectrum of broad-band lasers using narrow gain lines

The rate equation model is used to investigate the stimulated emission kinetics of broad-band multimode lasers in the presence of an additional gain a in various modes and over a wide time interval, taking into account the spontaneous radiation. Condensation of the spectrum exhibiting features of a phase transition is observed for an additional gain higher than a certain critical value. The quantitative characteristics of the effect are obtained. An analysis is made of the mechanism of appearance of an additional gain due to the lens-like properties of an intracavity gas-discharge cell. Estimates of a are given for various resonator configurations and a comparison is made with experiments.