Photorefractive photosensitizer

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. 

Chromophores with a rather high optical anisotropy are the merocyanines (77), especially in the cyanine limit with equal contributions of the apolar and zwitterionic resonance structures [319]. Thus, they also have been proposed as promising candidates for photorefractive systems based on molecular glasses. For 77, doped with a photosensitizer, a refractive index modulation of 0.01 at an electrical field of 22 V/pm was reported. 

J. Ortiz, F. Femandez-Lazaro, A. Sastre-Santos, J. A. Quintana, J. M. Vil-lalviUa, P. Boj, M. A. A. Diaz-Garcia, J. A. Rivera, S. E. Stepleton, C. T. Cox, andL. Echegoyen. Synthesis and electrochemical and photorefractive properties of new trinitrofluorenone-C-60 photosensitizers. Chem. Mater, 16(24) 5021-5026, November 2004. 

The first photorefractive polymer (77) was a guest/host system based on a partially cross-linked form of the electro-optic side-chain polymer bisA-NPDA (bis-phenol-A-diglycidylether (bis-A) and 4-nitro-l,2-phenylenediamine (NPDA)) doped with the transport agent DEH (diethylamino-benzaldehyde diphenylhydrazone). NPDA also provided photosensitivity. Simultaneously, we developed at the University of Arizona a flilly functionalized side-chain polymer that showed electro-... 

Within a relatively short time, many polymeric materials were developed that do exhibit the photorefractive effects. These materials consist of polymers with charge transport agents and photosensitizing dyes. The quantity of change in a material s refractive index that is altered by alterations in an applied electric field is expressed as the electrooptic coefficient r. Lithium niobate has an r value of 30 pm / volt. Several polymers are already known that possess coefficients (at 1.3 pm) greater than 30 pmW and the aim now is to develop materials with r values of 50 pm / volt or even higher. It is also known that the photorefractive effect can also be observed in many organic materials. 

K. Meerholz, Organic Photorefractive and Photosensitive Materials for Holographic Applications, 4802 SPIE, Bellingham, Wash., 2002. 

Synthesis and characterization of photorefractive polymers containing transition metal complexes as photosensitizer. J. Am. Chem. Soc., 119, 4622-4632. 

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. 

Winiarz JG, Prasad PN (2002) Photorefractive inorganic-organic polymer-dispersed liquid-crystal nanocomposites photosensitized with cadmium sulfide quantum dots. Opt Lett 27 1330-1332... 

Khoo, I. C., M. Y. Shih, A. Shishido, P.H. Chen, and M. V. Wood. 2001. Liquid crystal photorefractivity Towards supra-optical nonlinearity. Opt. Mater. 18 85-90 Khoo, 1. C., M. Y. Shih, M. V. Wood, and P. H. Chen. 2000. Extremely nonlinear photosensitive nematic liquid crystal film. Synth. Met. 7413 1-6. 

The high optical damage threshold, low dielectric constants, hi photosensitivity, and low cost of photorefractive polymers make them more efficient than inorganic materials (129). Optical data storage in PMMA-based photorefractive polymers has been demonstrated as a cheap and compact way improve data stoi age on compact discs and digital versatile discs (103). Polysiloxane-based photorefractive polymers have demonstrated the highest optical clarity and lowest optical scattering to date (105). 

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