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.

Chromophore orientational mobility and index grating rise time in azo-dye-doped photorefractive polymer composites

Abstract: The influence of chromophore solubility enhancements on photorefractive grating rise time and device lifetime is investigated. Three azo chromophores differing primarily in compatibility with a polyvinylcarbazole host polymer were synthesized. Aromatic substitutions to the chromophore increased the device lifetime from several days to years although electric-field-induced poling experiments indicated that chromophore orientational mobility is severely hindered, resulting in photorefractive grating rise times approaching several hours. The incorporation of a flexible butyl chain to the aromatic substituted chromophores significantly enhanced the orientational mobility. These chromophores could be loaded as high as 60wt% with no degradation in transparency for one year following fabrication.

Photorefractive effect in undoped aluminum nitride.

Abstract: We report our observation of the photorefractive effect in undoped aluminum nitride. We measured the coupling constant and the formation rate as a function of pump intensity at a wavelength of 405 nm in a two-wave mixing experiment. The photorefractive gain coefficient was 0.47 cm−1 at I = 6.9 W/cm2, and the actual saturated value was probably larger than this. The time constant was 59 ms at I = 1.0 W/cm2. In addition to a refractive index grating, an absorption grating was also formed, which is attributed mainly to an ionized trap density modulation process.

Molecular Engineering of Push-Pull Molecules: Towards Photorefractive Materials

Abstract: In low glass-transition temperature photorefractive materials, push-pull chromophores induce photorefractivity essentially via two mechanisms: optical birefringence and Pockels electrooptic effect. A 2-state 2-form description of these molecules indicates how the molecular structure can be optimized to maximize the photorefractive effect. At the optimum structure the two contributions have opposite signs. For the molecular sizes used currently the optical birefringence should dominate photorefractivity. Lengthening the conjugation path leads to a steeper increase of the Pockels electrooptic effect. Yet for the molecular sizes examined in this work, this contribution remains smaller than the optical birefringence at the optimum structure. Huge photorefractive responses could by attained if the molecular structure can be tuned towards the cyanine limit while increasing the molecular size.

Tunable color filter with surface plasmon resonance using organic photorefractive composite

Abstract: We report on a tunable color filter with surface plasmon resonance (SPR), excited by a photorefractive (PR) diffraction grating When a white light was incident at the diffraction grating formed by a PR effect, the SPR generated at a metal-dielectric material interface was absorbed, and the reflected light showed a complementary color When the period of the PR diffraction grating was modified by alteration of the optic configuration, the wavelength at which the SPR excitation led to a reflection minimum changed and the spectrum of the reflected light also changed A well-known equation was used to help us understand the experimental results All experimental results are in good agreement with the calculation predictions This result could lead to a new type of tunable color filter

Photorefractive semiconductor nanostructures

Abstract: Publisher Summary This chapter provides an introduction to photorefractive semiconductor nanostructures. They are nonlinear optical devices that alter their optical properties in response to time- and space-varying light intensity patterns. They are used to perform dynamic holography under ultra low-light intensities much smaller than those used for traditional nonlinear optical materials. These devices contain nanometer-scale features that enhance their optical properties and alter their electronic transport relative to bulk behavior. They also contain high densities of deep level defects that make the devices semi-insulating. These defects trap and store photogenerated carriers that accumulate into space-charge densities that match the intensity patterns. The trapped charge produces electric fields that modify the optical properties of the nanostructure. The translation of temporally and spatially varying light intensity patterns into physical changes in the optical properties of the material, matching the intensity patterns, is called the photorefractive process. There are several ways that electric fields can be applied to quantum-well structures, and several ways that optical beams can be incident on the devices to write holograms. The various configurations can be summarized by three basic fields and grating geometries. Two of the structures are transmission structures with the optical beams incident on the same face, and one is reflection geometry with the beams incident from opposite faces.