Two widely used methods of phase conjugation: four-wave mixing and stimulated Brillouin scattering (SBS) have been investigated. With 15ns pulsed Nd:YAG laser a reflectivity of 125% by degenerated four-wave mixing in silicon single crystal and a reflectivity of more than 80% by SBS in acetone or CS2 have been obtained. With the phase conjugate SBS-mirror a laser has been built, which compensates for phase aberration inside the laser resonator. Nonlinear optical phase conjugation is a newly developed technology in the region of nonlinear optic during the past seventeen years ' . With this technique we can get the wave front reversal of a given light wave, which is equivalent to performing the operation of complex conjugation on its complex spatial amplitude. 'Time-reversed" light waves can be used to improve laser-beam quality, compensate for atmospheric turbulence in optical systems or for the phase aberration caused by thermal effects at the high repetition frequency or by crystal defects in active laser media in solid state laser systems. Therefore a great interest has been shown and a good deal of investigations are being made in phase conjugation. In this paper we report the investigation on phase conjugation by four-wave mixing in silicon and SBS in fluids using l5ns pulsed Nd:YAG laser. Furthermore we have built a laser resonator with a SBS-cell inserted in a laser resonator, which has emitted laser pulses with 5ns pulse duration and 130mJ pulse energy. Elimination for phase aberration has been proved by insertion of an etched glass plate into the cavity.
"Phase conjugation using Nd:Yag laser", Proc. SPIE 1230, International Conference on Optoelectronic Science and Engineering '90, 12303V (1 July 1990); doi: 10.1117/12.2294776; https://doi.org/10.1117/12.2294776