Photorefractive crystals

Phase Materials. Phase holograms can be recorded in a large variety of materials, the most popular of which are dichromated gelatin, photopolymers, thermoplastic materials, and photorefractive crystals. Dichromated gelatin and some photopolymers require wet processing, and thermoplastic materials require heat processing. Photorefractive crystals are unique in that they are considered to be real-time materials and require no after-exposure processing. 

Buchnev O, Glushchenko A, Reznikov Y, Reshetnyak V, Tereshchenko O, West J (2003) Nonlinear optics of liquid and photorefractive crystals 5257 7... 

Within inorganic photorefractive crystals the optical generation of carriers is associated usually with the oxidation of defect and impurity states within the optical band gap of the crystal, such as iron impurity within lithium niobate crystals, as in Figure 9. 

Petrov, M. P., Stepanov, S. I., Khomenko, A. V. Photorefractive Crystals in Coherent Opucal Systems. Berlin Springer, (1991). 

Various materials such as photopolymers, photorefractive crystals, photochromic materials, and polarization sensitive materials can store data. Among these materials, photorefractive recording media in which data are stored as refraaive-index change are the most promising in 3D memory because they have little absorption hence, the light penetrates into the deep layers in the media. 

M.P. Petrov, S.L. Stepanov, A.V. Kho-menko, Photorefractive Crystals in Coherent Optical Systems, Springer, Berlin (1991). 

For several decades, the fields of photoconducting (75) and purely electrooptic polymers (74) have been very active but had almost no direct overlap. With the development of photorefractive polymers in the early nineties, the knowledge of these two research areas could be combined and has led to a rapid improvement of the performance of existing photorefractive polymers. The photorefractive polymer composite DMNPAA PVK ECZ TNF (DMNPAA 2,5 -dimethyl-4-(p-nitrophenyl-azo)anisole PVK poly(N-vinylcarbazole) ECZ N-ethylcarbazole TNF 2,4,7-trinitrofluorenone) we developed recently (P) has reached a level of performance that competes with that of the best inorganic photorefractive crystals (77,72). With the recent progress achieved in the development of new chromophores for electro-optic applications (75), the efficiency of these new materials is expected to be significantly further improved. 

The purpose of this work is to present, in a plain way, the use of a photorefractive crystal as holographic recording material. The hologram consists in the interference between diffraction free beams. The interest in this topic comes from the fact that in the physical optics context, a contemporary topac research consists in the trapping and manipulation of particle conductors or/and dielectrics by means of optical fields also as atom/ ion trapping... 

Unnikrishnan G. Joseph J. Singh K (1998). Optical Encryption System that Uses Phase Conjugation in a Photorefractive Crystal, App. Opt, Vol.37, pp.8181-8186 Yamazaki M. Ohtsubo J. (2001). Optimization of Encrypted Holograms in Optical Security Systems, Opt. Eng., Vol.40, pp.132-137... 

Other recording materials include dichromated gelatin, elastomers, photoreactive polymers, photochromies, photorefractive crystals, photoresists,... 

G, V. Klimusheva and A. G. Iljin, eds.. Eighth International Conference on Nonlinear Optics of Liquid and Photorefractive Crystals, 4418 SPIE, Bellingham, Wash., 2001. 

J., Tschudi, T., Chamrai, A.V., Bryksin, V.V., and Petrov, M.P. (2003) Optical on-line controllable filters based on photorefractive crystals. J. Opt. A Pure Appl. Opt., 5, S471-S476. 

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