Four-wave mixing in resonantly amplifying media in the inversion saturation regime

TLDR: In this article, a theoretical analysis of four-wave mixing in the active medium of a laser whose radiation wavefront is to be reversed is presented, where explicit allowance is made for changes in the amplitudes of the pump waves as a result of their amplification during propagation in an active medium.

Abstract: The two-level approximation is used to make a theoretical analysis of four-wave mixing in the active medium of a laser whose radiation wavefront is to be reversed. Explicit allowance is made for changes in the amplitudes of the pump waves as a result of their amplification during propagation in the active medium. Both the completely degenerate case, when the frequencies of all four waves are the same, and the case of a small detuning of the signal wave frequency relative to the pump waves are considered. For the completely degenerate case a system of reduced equations allowing for saturation of the inversion was solved by computer using an iterative method. It was found that, under optimum conditions in the saturation regime, the power of the wave reflected from a four-wave mixer may be higher than that of the signal wave.