5.3.2. Traps and Grating Dark Decay 3288 5.3.3. Other Concerns 3288 6. New Photorefractive Materials 3289 6.1. Polymer Composites 3289 6.2. Organic Amorphous Glasses 3292 6.3. Fully Functionalized Polymers 3294 6.4. Polymer-Dispersed Liquid Crystals 3295 6.5. Other Liquid Crystal-Containing Materials 3296 6.6. Near-Infrared-Sensitive Materials 3297 6.7. Other Materials Directions 3298 6.7.1. Hybrid Organic−Inorganic Composites and Glasses 3298

Organic photorefractives: mechanisms, materials, and applications.

Considerable progress has been made in organic photorefractive materials, since the first observation of photorefractive phenomena from organic materials. Within recent years, a large number of organic photorefractive materials, especially amorphous materials, have been developed based on polymeric composites, fully functional polymers and the multifunctional chromophore approach. Among these organic photorefractive materials, some of them containing carbazole components as a charge transporting function have been demonstrated to exhibit high performance photorefractive effects. The carbazole building blocks with charge transporting functionality or multifunctions play a very important role in photorefraction and have been widely used in the molecular design approach to new organic photorefractive materials. Based on carbazole functional building blocks, amorphous multifunctional chromophores, amorphous monolithic chromophores and amorphous dendrimers have also been developed as new types of organic photorefractive materials. This paper reviews the recent progress of organic photorefractive materials, especially organic photorefractive materials containing carbazole functional components.

Carbazole photorefractive materials

Molecular materials for second‐order nonlinear optical applications

This chapter reviews different suggestions for applications of PRCs. Due to the high sensitivity, high diffraction efficiency, reversibility, and the ease of handling, these dynamic photosensitive media attracted the attention of researchers working in different areas of coherent optics. Early proposals on the use of photorefractive crystals and SLMs for holographic interferometry and 2D image processing are still interesting. Recently, a number of new ideas on PRC applications based on various phase-conjugate geometries have appeared, too.

http://iopscience.iop.org/article/10.1088/0034-4885/57/1/002/pdf

Applications of photorefractive crystals

We consider holographic optical data storage systems implemented with photorefractive media. Our viewpoint emphasizes the close interaction between materials and device issues. First we discuss our current understanding of photorefractive physics as it pertains to the holographic data storage problem. Then we consider architecture issues, including angular, phase-encoded, and wavelength-multiplexing techniques, and several approaches to increasing the signal-to-noise ratio of the recordings. Finally, we discuss materials issues related to crystal growth and how crystal quality impacts the performance of data storage systems. Both bulk and fibre crystal growth techniques are reviewed.

Optical memories implemented with photorefractive media

We survey the dynamics of the photorefractive effect in a methyl methacrylate copolymer with the nonlinear chromophore p-nitroaniline in a pendant side group doped with a charge-transport agent, diethylaminobenz-aldehyde diphenylhydrazone, a material that represents a new class of photorefractive polymer. The grating growth times are several orders of magnitude smaller than that for the previous epoxy-based photorefractive polymers and fall below 1 s at the highest intensities used. Grating competition and revelation effects suggest that charge carriers other than photogenerated holes are mobile. A sublinear dependence of growth rate on writing intensity implies that shallow traps may also be present.

Subsecond grating growth in a photorefractive polymer

A synthetic approach for the preparation of poly(aryl ether phenylquinoxalines) has been developed wherein the generation of an aryl ether linkage is the polymer-forming reaction. Fluorines located on the pare position of the benzene rings of various 2,3-diphenylquinoxaline heterocycles were found to be activated toward nucleophilic aromatic substitution. Model reactions demonstrated that these fluorine atoms on the phenyl groups of the diphenylquinoxaline were displaced by phenoxides in high yield, and the process was deemed suitable as a polymer-forming reaction. Thus, the pyrazine component of the phenylquinoxaline heterocycle has an activating effect on both the annulated benzo ring and the pendant phenyl groups, albeit to a lesser extent in the latter case

Heterocycle-activated aromatic nucleophilic substitution: poly(aryl ether phenylquinoxalines). 2

New high temperature poly(aryl ether oxazoles) [OPh-(C 3 NO[PhSO 2 Ph])-PhOPh-X-Ph] n (X= CO, SO 2 ) are synthesized by nucleophilic substitution polycondensation. Theese polymers exhibit good stability of poled order at high temperatures

Synthesis and Characterization of Main-Chain High-Temperature Nonlinear Optical-Active Polymers. Poly(aryl ether-oxazoles)

Poly(aryl ether benzazole)s: Self-Polymerization of AB Monomers via Benzimidazole-Activated Ether Synthesis

The photorefractive effect has been recently observed by holographic grating formation in optically non-linear polymers molecularly doped with charge transport agents. Grating formation can be understood as a four-step process, the first three of which dictate the photoconductive response: charge generation, mobility and trapping. The fourth step is modulation of the refractive index by the resulting space-charge field, via the electro-optic effect. We present the results of photoconductivity experiments to determine charge generation efficiency, carrier mobility and the kinetics of recombination and trapping, focussing primarily on the epoxy polymer bisphenol-A-diglycidylether 4-nitro-1, 2-phenylenediaminc (bisA-NPDA) doped with the hole transport agent, diethylaminobenzaldehyde-diphenylhydrazone (DEH). The electric field dependence of the generation efficiency and mobility differ in detail from results on other molecularly doped polymers.

T. J. Matray

Papers

Subsecond grating growth in a photorefractive polymer

Heterocycle-activated aromatic nucleophilic substitution: poly(aryl ether phenylquinoxalines). 2

Synthesis and Characterization of Main-Chain High-Temperature Nonlinear Optical-Active Polymers. Poly(aryl ether-oxazoles)

Poly(aryl ether benzazole)s: Self-Polymerization of AB Monomers via Benzimidazole-Activated Ether Synthesis

Photoconductivity of Photorefractive Polymers