Chapter 11 - The Electrooptic and Photorefractive Effects

Abstract

The electrooptic effect is the change in the refractive index of a material induced by the presence of a dc (or low-frequency) electric field. In some materials, the change in refractive index depends linearly on the strength of the applied electric field. This change is known as the linear electrooptic effect or Pockels effect. Linear electrooptic effect can occur only for materials that are noncentrosymmetric. Although the linear electrooptic effect can be described in terms of a second-order nonlinear susceptibility, a very different mathematical formalism has historically been used to describe the electrooptic effect. The photorefractive effect is the change in refractive index of an optical material that results from the optically induced redistribution of electrons and holes. The photorefractive effect is quite different from most of the other nonlinear-optical effects. The photorefractive effect tends to give rise to a strong optical nonlinearity. Moreover, under certain circumstances, two beams of light can interact in a photorefractive crystal in such a manner that energy is transferred from one beam to the other. This process, which is often known as two-beam coupling, can be used to amplify a weak, image-bearing signal beam by means of an intense pump beam.