Hologram erasability, photorefraction

A recording technique of holograms and the non-destructive readout in a photorefractive polymer, utilizes two-photon absorption. The holograms are formed through the photorefractive effect. The technique uses the excitation of the electroactive chromophore with femtosecond pulses, followed by charge injection into a PVK matrix. The holograms can be fully erased with a pulsed laser beam. However, they are insensitive to continuous wave laser beams with the same wavelength. 

Photorefractive materials have attracted considerable interest because of their potential applications in electro-optic devices, e.g., for holograms, optical computing, or as storage media for erasable read-write optical memories. As their name implies, photorefractive materials are photosensitive and have an electric field-dependent refractive index. 

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