Spectral behavior of amplified back-scattered Stokes pulse in two-cell phase conjugating mirror

In this paper, the spectral behavior of two-cell phase conjugating mirror (PCM) with a two-pass Nd:YAG amplifier has been analyzed experimentally and theoretically. For this purpose, input intensity with single and multi-longitudinal modes has been investigated. The numerical model is based on focused geometry model (1+1 dimension) equations of Stokes back-scattered intensity and acoustic waves, for two-cell generator-amplifier phase conjugating mirror with proper boundary conditions that are solved simultaneously with the rate equations of Nd:YAG optical amplifier. Results of the Fourier analysis of the amplified intensity show considerable differences between Fourier amplitudes of the amplifier equipped with PCM and a two-pass amplifier with a conventional mirror under the same output energy. The amplifier with PCM has a completely filtered and different spectral behavior with clearly reduction of the beating between Fourier components of input optical field. Calculations show that the filtering of Fourier components by a PCM is done more effectively with lower pumping energy.