Electromechanical and optical effects in photorefractive materials

From thermodynamic considerations, we derive a consistent set of equations coupling the steady-state photoinduced photorefractive space-charge field to mechanical deformations, dc permittivity, and refractive index changes. For the first time to our knowledge, these equations include piezoelectricity, electrostriction, the elasto-optic effect, the linear and quadratic electro-optic effects, as well as the influence of the volume forces and electric torques. We determine the conditions on the material parameters, for which volume forces and torques are of some importance on the optical properties. These equations resulting from a macroscopic approach are valid whatever the physical microscopic origins of the various effects. Non centrosymmetrical and centrosymmetrical materials are considered. The order of approximation is the lowest possible able to describe the mentioned effects in both types of materials. Received: 18 November 1998 / Revised version: 18 February 1999 / Published online: 12 April 1999