Noise of four-wave hypersonic wavefront-reversing mirrors under absolute instability conditions

A calculation is made of the noise of four-wave hypersonic wavefront-reversing mirrors under absolute instability conditions. An analysis made using the approximation of a constant field of the pump waves in the absence of wave mismatch shows that the sensitivity of such mirrors deteriorates on increase in the excess above the instability threshold. Estimates are made of the lowest power of weak signal waves at which it is still possible to separate the reversed signal from the background of the noise in the nonlinear medium of the wavefront-reversing mirrors.