[en] We report the three-dimensional simulation results of phase conjugation upon nonstationary stimulated Brillouin scattering of a focused laser beam. It is shown that in the case of deep focusing of laser radiation in the SBS cell, the phase conjugation quality decreases with increasing laser power and reflection coefficient, in agreement with experimental results. In calculations, the process of Stokes radiation generation is studied in detail, the reasons for a decrease in the phase conjugation quality are explained, and a means of its improvement is proposed. (nonlinear optical phenomena)

[en] The phase conjugation (PC) of a focused Gaussian laser beam with a partial spatial coherence of the wave front is studied numerically and theoretically upon SBS within the framework of a three-dimensional nonstationary SBS model, which takes into account transient processes and SBS saturation. The dependences of the PC coefficient h on the laser radiation power are obtained for different excesses of the angular divergence over the diffraction limit ξ. It is found that for the given reflectance of laser radiation from the SBS mirror, the PC coefficient monotonically decreases with increasing the divergence. For example, under the near threshold SBS conditions, h decreases from 70% to 30%, when ξ increases from 1 to 10. For the given divergence, the PC coefficient increases with increasing the reflectance and approaches the ideal one (h > 90%) upon deep SBS saturation, when the reflectance exceeds 90%-95%. (nonlinear optical phenomena)

[en] We study experimentally stimulated Brilluoin scattering (SBS) of vortex laser beams, namely, the LG₁¹ and LG₀¹ Laguerre -Gaussian modes. The wave front transformation is experimentally demonstrated in the case of SBS of the LG₁¹ laser mode, directly focused into the SBS cell, when the fundamental Gaussian mode LG₀⁰ rather than the conjugate mode is selected from the Stokes beam. It is shown that optical vortices become phase conjugate by destroying the laser mode structure in the SBS cell. Phase conjugation (PC) of the LG₀¹ and LG₁¹ modes is obtained in the SBS mirror using a regular aberrator (microlens raster) in the system of laser beam focusing into the SBS cell.

[en] We investigated the phasing of pulsed two- and fourchannel laser beams due to phase conjugation upon transient stimulated Brillouin scattering (SBS) in a double-pass amplification scheme. A high quality of beam phasing was experimentally demonstrated with the use of a microlens raster and an angular selector in the SBS-mirror scheme. The data obtained in the numerical simulation of transient SBS are in good agreement with experimental ones.