Four wave acousto-electromagnetic interactions in crystals with a nonlinear electrostriction

The four wave parametric interactions of microwave acoustic waves with powerful electromagnetic radiation in the strong nonlinear regime is investigated. The interaction is due to account of the fourth order terms in the expansion of the free energy of the anisotropic crystal. It is shown, that the instability and the parametrical increasing of the waves' amplitudes in a system takes place. This leads to shaping of the spatially inhomogeneous structures. The velocity of propagation of those structures is smaller than the sound velocity in such a crystal.