Influence of piezoelectricity on the photorefractive effect

We demonstrate that the spatially modulated electric field that is associated with a photorefractive grating generates stress and strain components with symmetries that are different from those induced by a uniform electric field. Therefore, because of piezoelectricity and the elasto-optic effect, the symmetries of the effective dielectric and electro-optic constants to be used to describe the photorefractive effect differ from the symmetries of the usual dielectric and electro-optic tensors. We derive analytical expressions to be used to compute these new constants from the measured clamped and unclamped dielectric and electro-optic coefficients. Experimental evidence is presented.