Breaking of the electrooptic and dielectric tensor symmetries by space charge electric fields

Abstract

The space charge electric field associated with a photorefractive grating generates deformations (through piezoelectricity) which in turn, modify both the electrooptic and dielectric constants. These modifications are of importance and must be taken into account1. For instance, in BaTiO3 samples the dielectric constant ϵ11, determined using spatially uniform applied electric fields, varies by a factor of two between clamped and unclamped crystals. Hereafter, we demonstrate that these differences are even more important for space charge electric fields because these non uniform fields induce strain components which are not produced by uniform fields. Therefore, the effective electrooptic coefficient can be different from zero in a configuration in which both the clamped and unclamped coefficients for uniform fields vanish.