Light-induced charge transfers between defects in photorefractive materials

The basic features of the photorefractive effect in oxide materials are out lined and the required knowledge on defects in such compounds is defined. T he central question is: Between what charge states of what defects does an inhomogeneous light pattern redistribute charges in a photorefractive cryst al? The joint investigation of light-induced EPR and optical absorption cha nges is introduced as a very useful method to answer this question, also fo r EPR-silent defect valencies and also at room temperature. Examples for th e application of the method are given and its scope is discussed.