  The model of nonlinear interaction of proper waves of photonic crystal with
plane acoustic wave was developed. The formulation of the model is reduced to
the eigenvalue problem, which can be solved by computer simulations. By means
of the formulae given in present paper one can predict which polarizations of
acoustic wave can result in Bragg diffraction of optical waves of TE or TM
polarizations. Computer simulation allows obtaining amplitudes of interaction
waves in the case of Bragg diffraction when phase-matching conditions are
fulfilled.
