Dynamic Holography Effects in Ferroelectrics Induced by Spatially-Oscillating Photovoltaic Currents

It’s well known that the main mechanisms of holographic grating formation in photorefractive crystals are the diffusion of carriers, their drift in the electric field, and the photovoltaic effect (PVE). We shall concentrate on the last mechanism. It’s often supposed that the PVE in ferroelectrics can be characterized by the current along the polar c→-axis, j=α G I, where α is the absorption coefficient, G: the Glass coefficient, I: the light intensity. In this case, the PVE effect is analogous to the effect of supplementary electric field E ph =j(σ d +σ ph )− 1 , where σ d , σ ph are dark- and photoconductivity. The photoinduced field E ph reaohes 10 5 v/cm in LiNbO3 and LiTaO3. However, the effect of the PVE does not come to longitudinal current.