Two-color holographic recording scheme allowing non-volatile reading in Mn:YAlO/sub 3/

Summary form only given.Inhomogeneous illumination of LiNbO/sub 3/ crystals yields refractive index changes by the so-called photorefractive effect. In this effect electrons are excited from traps into the conduction band, the free charge carriers migrate towards the darker regions, space-charge patterns and electric fields build up, and these fields modulate the refractive index via the electro-optic effect. Important measures for the photorefractive performance are the saturation value of the refractive index changes as well as sensitivity and persistence. The sensitivity determines how much light is required to build the refractive-index changes up, and persistence is a critical issue, because homogeneous illumination redistributes the charge carriers back and erases the refractive index patterns. Recent improvements of all these parameters were achieved by modifications of the material, and a review will be given in the talk.