Add to ORKGThe photorefractive effect is observed in materials which are both electrooptic and photoconducting. When a light pattern is incident on such a material, charges that are photogenerated in the illuminated regions, migrate and eventually get trapped at the dark regions of the sample. The resulting charge redistribution creates an internal electric field, the space charge field, which changes the refractive index via the electrooptic effect. In this way, a refractive index hologram which is a replica of the illumination pattern is created. ... Zie: Summar