The influence of surface states and light attenuation on transient phenomena in photorefractive films

The distribution of free electrons and the formation of the electric field from the dark condition are analysed in an insulator-photorefractive (PR) f ilm-insulator sandwich illuminated by a single optical beam in the absence of an external electric field. Boundary conditions are derived that take in to account the dynamics of fast surface states. The mathematical solution f or the transient process is obtained, based on the well known transport equ ations of photorefractive theory. The role of surface states and attenuatio n is discussed. In particular, it is shown that the character of transients in the boundary depletion layers depends on the ratio of the charged surfa ce state lifetime to the dielectric relaxation time. It is also shown that the width of the depletion layers varies with time if the diffusion length differs from the Debye length.