Determination of the optimal concentrations of active particles in laser media

A method is proposed for the determination of the optimal concentration of an active impurity from the point of view of maximizing the population of the upper active level in both cw and pulsed regimes at a low optical density of the laser active medium. It is shown that the dependence of the population on the concentration changes qualitatively with the law governing concentration quenching of the luminescence. For example, if decay of the excited state takes place in the kinetic limit (if the rate of nonradiative relaxation is linear with respect to the concentration of energy acceptors and does not depend on the donot concentration), concentration quenching of the luminescence does not limit the concentration of active particles in the active element The proposed method is illustrated by calculating optimal concentrations of neodymium tons in a YAG crystal for cw and pulsed regimes.