Photorefractive holographic storage

Complete erasing of the recording information can be completely erased by ultraviolet illumination. Dual-use chromophore molecules allow to write both irreversible photochromic and erasable photorefractive holographic gratings into the same storage volume. ... 

Materials. For holographic information storage, materials are required which alter their index of refraction locally by spotwise illumination with light. Suitable are photorefractive inorganic crystals, eg, LiNbO, BaTiO, LiTaO, and Bq2 i02Q. Also suitable are photorefractive ferroelectric polymers like poly(vinyhdene fluoride-i o-trifluorethylene) (PVDF/TFE). Preferably transparent polymers are used which contain approximately 10% of monomeric material (so-called photopolymers, photothermoplasts). These polymers additionally contain different initiators, photoinitiators, and photosensitizers. 

A major application of photorefractive polymers as holographic data storage media is a real possibility. In this application two interfering laser beams write a hologram... 

Hessehnk, L., Orlov, S.S., Liu, A., Akella, A., Lande, D., and Neurgaonkar, R.R., Photorefractive materials for nonvolatile volume holographic data storage, Science, 282, 1089, 1998. 

B. Kippelen, Overview of Photorefractive Polymers for Holographic Data Storage, in J. Coufal, D. Psaltis, G.T. Sincerbox (eds.), Holographic Data Storage,... 

We have prepared multi-component photorefractive polymers for optical data storage applications (8). This photorefractivity is a combination of two functionalities electro-optic effect and photoconductivity. We have achieved holographic diffraction efficiencies up to >30% in our composites. 

Optical Devices. Of most interest in this application are those studies related to the nonlinear optical effects in polyphosphazene derivatives bearing aromatic azo imits (217-219) and the photorefractive effect with pol5q)hosp-hazenes bearing carbazolyl substituents (220). Possible applications include optical switches, frequency doublers for lasers, holographic data storage, and real-time image processing. 

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