ABSTRACT

Photorefractive effect is literally understood as a phenomenon that the refractive indices of materials are changed when they are illuminated by light. There are many possible ways that present the similar phenomena but usually the term photorefractive effect is used in the limited sense, i.e., the light-induced index change in electrooptic materials where the space charge field is formed by the illumination of nonuniform light intensity. This effect has been first discovered in lithium niobate and lithium tantalate [1], but it was soon recognized that this is commonly observed in a large family of electrooptic materials [2]. Now, photorefractive materials are classified into four groups:

(1) ferroelectric oxides (LiNb03, BaTi03, SrxBr1_xNb206, KNb03, etc.), (2) cubic oxides (sillenites such as Bi12Si02o), (3) compound semiconductors (GaAs, InP, etc.), and (4) organic materials (polymers and crystals).