Self-diffraction and stimulated Brillouin scattering of opposite light waves in absorbing media

A study was made of the characteristics of self-diffraction of opposite optical waves in the case of a thermal mechanism of grating formation. The main factor limiting the self-diffraction efficiency was found to be a low-threshold absolute instability of the optical wave due to stimulated Brillouin scattering. The conditions were found under which the radiation generated by stimulated Brillouin scattering had a high spatial and temporal coherence.