Dynamic self-focusing of a Gaussian light beam accompanying saturation of an inhomogeneously broadened absorption line

It was found experimentally that when a Gaussian laser beam interacts with a Doppler broadened absorption line in a gas, under conditions of saturation, a dynamic self-focusing of the beam is manifested as a transient process if the radiation frequency varies with time. This effect was studied experimentally in CO₂/OsO₄ and CO₂/SF₆ lasers in the presence of sinusoidal frequency modulation of the laser radiation. The dynamic self-focusing was maximal when the modulation frequency was comparable with the homogeneous line width. This effect was a destabilizing factor in lasers stabilized by saturated absorption.