This is the first of two volumes that review, for the first time, all major aspects of photorefractive effects and their applications. Photorefractive effects in electro-optic crystals are based on optically induced space-charge fields which ultimately alter the refractive indices by the electro-optic Pockels effect. The fundamental phenomena leading to photoinduced changes of refractive index, the materials requirements and experimental results on a variety of photorefractive materials are discussed and the most recent theoretical models describing these phenomena are presented. Interest in...