Transients in light illuminated photorefractive sandwiches in the presenceof surface states and of a d.c. voltage

The response of an insulator-photorefractive film-insulator sandwich is inv estigated to an input optical beam in the presence of an applied d.c. volta ge. First the optical beam is switched on which generates free carriers and causes the appearance of an electric field. Having reached a steady state a voltage is then applied to the sandwich, and the subsequent behaviour of the electron density and of the electric field is analysed as a function of time and space subject to boundary conditions which take into account the dynamics of fast surface states. The mathematical solution obtained describ es both the short-time limit when a quasi-steady electron distribution is f ormed and the long-time limit when the electric field is screened. The role of surface states and that of the attenuation of the optical beam is discu ssed. (C) 2000 Elsevier Science B.V. All rights reserved.