  The lateral shift of an optical beam undergoing a Brillouin light scattering
on acoustic wave in the total internal reflection geometry is studied
theoretically. It is shown that the lateral shift depends on polarization
(longitudinal or transversal) of the acoustic wave, as well as on the type of
the scattering process: direct one, when the scattered wave undergoes a lateral
shift at reflection from the interface, and cascading one, when
fundamental-frequency light beam is laterally shifted at reflection and then is
scattered on the acoustic wave.
