Organic photorefractive materials

About: Organic photorefractive materials is a research topic. Over the lifetime, 697 publications have been published within this topic receiving 13041 citations.

Carbazole photorefractive materials

Abstract: 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.

High-speed photorefractive polymer composites

Abstract: Two photorefractive polymer composites are presented that exhibit the fastest response times reported to date by an order of magnitude (τg≈5 ms at 1 W/cm2), while maintaining large gain coefficients (Γ≈230 and 130 cm−1). These materials show promise for video-rate optical processing applications. The factors limiting the photorefractive speed in these materials are investigated.

Use of two-photon absorption in a photorefractive crystal for three-dimensional optical memory

Abstract: We describe the use of two-photon absorption in a photorefractive crystal for recording bit data in multilayered optical memory. A short-pulse near-infrared laser is used for generating the photorefractive effect by two-photon absorption. We succeeded in recording and reading seven layers of data in a LiNbO3 crystal with a lateral resolution (distance between bits) of 5 µm and an axial resolution (distance between layers) of 20 µm.

Franz-Keldysh Effect of the Refractive Index in Semiconductors

Abstract: Changes in the shape of the fundamental absorption edge of a semiconductor as induced by strong electric fields will lead to correlated changes in the refractive index. Computation of the dispersion integral for an absorption edge that is modified by the Franz-Keldysh effect proves that the refractive index of germanium and gallium arsenide changes by as much as 0.02, for instance, for electric fields characteristically present in a $p\ensuremath{-}n$ junction. The fact that the refractive index depends upon electric fields extends the Franz-Keldysh effect to reflection phenomena, even if this refractive index is much greater than the extinction coefficient, which is usually the case near the fundamental edge of semiconductors. Based on this dependence of the refractive index upon electric fields, the field effect of the reflectance in germanium is interpreted and good agreement is obtained with experiment. It is pointed out that this mechanism could be relevant for the confinement of the radiation in a gallium arsenide laser.

A photorefractive organically modified silica glass with high optical gain

Abstract: Photorefractive materials1 exhibit a spatial modulation of the refractive index due to redistribution of photogenerated charges in an optically nonlinear medium. As such, they have the ability to manipulate light and are potentially important for optical applications1 including image processing, optical storage, programmable optical interconnects and simulation of neural networks. Photorefractive materials are generally crystals, polymers and glasses with electro-optic or birefringent properties and non-centrosymmetric structure2. Here we report the photorefractive effect in both non-centrosymmetric and centrosymmetric azo-dye-doped silica glasses, in which refractive index gratings that are spatially phase-shifted with respect to the incident light intensity pattern are observed. The effect results from a non-local response of the material to optical illumination, and enables the transfer of energy between two interfering light beams (asymmetric two-beam coupling). Although the writing time for the present grating is relatively slow, we have achieved a two-beam coupling optical gain of 188 cm-1 in the centrosymmetric glasses, and a gain of 444 cm-1 in the non-centrosymmetric structures. The latter are fabricated using a corona discharge process3 to induce a permanent arrangement of azo-dye chromophores.