Defects in Inorganic Photorefractive Materials and Their Investigations.

The role of defects in the photorefractive effect is known in principle: their photoionization in the brighter regions of a photorefractive crystal, illuminated by an inhomogeneous light pattern, causes quasifree charge carriers. These are separated from their home sites by diffusion, by the bulk photovoltaic effect, or by drift in an external electric field. Eventually they are trapped at empty levels of defects in the darker regions, and a space charge field is created. Crystals with a linear electrooptic effect transform this into a refractive index pattern. Theoretically, also the rates of the ionization process, the transport, and the trapping can be formulated quantitatively. This chapter gives information on how this general picture may be filled by real defects in existing photorefractive crystals. [ABSTRACT FROM AUTHOR]