Abstract

The band-transport model is used to study the effects of a cw Gaussian laser beam on photorefractive materials. Particular attention is paid to differences in behavior of the material with and without an applied electric field. In the steady state, without an applied electrical field, the effects of the light intensity, beam width and the photovoltaic term are discussed. The inclusion of the thermally excited carrier background is shown to be necessary in order to obtain reasonable physical results. When the intensity is low enough, our results agree with previous work in this area. When a de electric field is applied, the field in the illuminated area of the crystal is significantly below the applied field value. This results from the movement of the carriers under the influence of the external field. Outside of the illuminated area and near the electrodes the field is enhanced as a result of the power supply maintaining a constant potential difference between the electrodes. On the other hand, the application of an ac field amplifies the field in the illuminated region. This effect may be useful in enhancing the electro-optical effect, as well as other nonlinear optical effects.

© 1990 Optical Society of America