Theory of Nonlinear Effects in a Gas Laser Amplifier. II. Strong Signals

Abstract

The model given in the preceding paper is used to calculate the nonlinear gain and phase of a laser amplifier operating at field intensities that may be too large for the perterbational results to be valid. The induced polarization is calculated exactly by integrating the macroscopic density-matrix differential equations. The incremental gain and phase shift are found to be complicated functions of the circularly polarized field intensity components. Simple physical interpretations of these functions are given. The results are used to compute the change in the ellipticity of a single-frequency signal in a high-gain amplifier.