Аннотация:We report the results of the analysis of the elastic field structure and the changes in optical permittivity tensor at optical frequencies in the region near the Z-plane of the BaTiO3 crystal. The assumption of given interference light pattern with a fringe spacing (Lambda) and an independent on z modulation index m at steady-state is used. The photorefractive grating vector K lies in the plane passing through Z-axis of the crystal and making an angle of (theta) with the X-axis. Taking crystal surface to be traction free we consider two cases: (a) dielectric boundary and (b) short-circuited boundary.