Аннотация:The surface properties of photorefraction crystals (PRC) within the appendices of a dynamic holography are of great interest. The availability of a nonuniformity of photorefraction grating in frontier area of PRC results both in quantitative, and qualitative features of modulation of optical properties of a crystal. In the paper the structure of photorefraction grating close to mechanically and electrically free border of crystals of the sillinites class with the applied external steady electrical field in steady-state conditions approaching the given distribution of photoexcited electrons in a conduction band is considered.