Organic and Inorganic Photorefractive Materials

The photorefractive effect as space-charge induced refractive index changes in inorganic electro-optic crystals and ceramics has been investigated extensively during almost three decades. In organic crystals the same effect had been discovered in COANP:TCNQ in 1989 [1]. Later on , three other organic crystals prepared in our laboratory have been shown to be photorefractive [2-4]. In addition to the photorefractive effect a similar effect due to the formation of space-charge induced orientational gratings has been found in poled polymers by several authors. Since the origin of the refractive index changes had not been recognized properly at the beginning, this effect was also called "photorefractive".