Sandalphon

Bio: Sandalphon is an academic researcher from University of Arizona. The author has contributed to research in topics: Photorefractive effect & Diffraction efficiency. The author has an hindex of 3, co-authored 4 publications receiving 693 citations.

A photorefractive polymer with high optical gain and diffraction efficiency near 100

Abstract: PHOTOREFRACTIVE materials are of considerable interest for the development of all-optical devices1. The photoref ractive effect appears in materials that exhibit an electric-field-dependent refractive index and that are photosensitive, such that the spatial distribution of photogenerated charge carriers is modified on irradiation with light. The diffraction pattern formed by the interference of two coherent light beams within such a material generates a non-uniform internal electric field that in turn modulates the refractive index. The resulting refractive-index pattern forms a grating that can diffract light and thereby give rise to two-beam coupling, whereby one of the writing beams gains energy at the expense of the other—a property that can be exploited in photonic devices. Although the best photorefractive materials currently available are inorganic crystals such as LiNbO3, there is considerable interest in the development of photorefractive polymers2–8, owing to their structural flexibility, ease of processing and lower cost. We describe here a polymer composite with excellent photorefractive properties. We have achieved a diffraction efficiency approaching 100% and a net two-beam coupling gain of more than 200 cm–1, making these polymeric materials suitable for immediate application in areas such as dynamic holographic storage and optical information processing1.

New highly efficient photorefractive polymer composite for optical-storage and image-processing applications

Abstract: Reversible holographic storage and beam amplification has been achieved in a new polymer composite using a low-power semiconductor visible laser diode emitting at 674nm. This material shows substantially better performance than the existing photorefractive polymeric materials. A diffraction efficiency of 5%, a gain coefficient of 30cm−1 and a net gain of 6cm−1 have been measured in 105 μm-thick samples with an applied field of 40V/μm.

Photorefractivity And Photoisomerization In Azo-Dye-Doped Polymers

Abstract: The photorefractive properties of photoconducting polymers doped with nonlinear azo dyes are investigated by means of polarization and field-dependent four-wave mixing experiments. The nonlocal response of the photorefractive effect is shown by two-beam coupling experiments. High diffraction efficiencies (> 5%) and net coupling gain (6 cm−1) are demonstrated at low power with a semiconductor laser diode in 105 μm films. Under some conditions, gratings due to photoisomerization of the azo dye molecules are also present and their properties are discussed.

Ultrafast Excited-State Dynamics in a Fluoro-Aluminum Phthalocyanine Thin Film

Abstract: Using femtosecond pump-probe spectroscopy, bleaching of the π-π* absorption Q-band, and photo-induced absorption on the high energy side of the Q-band, have been observed and time-resolved in a nearly-amorphous thin film of fluoro-aluminum phthalocyanine. Following excitation, the induced absorption signal develops as the absorption saturation signal diminishes, suggesting exciton decay into a subgap state. The different bimolecular decay dynamics observed for the absorption saturation (τ eff ≈700 fs) and induced absorption (τ eff ≈ 2 ps) signals support this conclusion. Possible origins of the subgap state are discussed. In addition, polarization-dependent spectral hole burning is observed at very early times. These results suggest the need for exploration of thin phthalocyanine films which are ordered in three dimensions over distances of at least 200–300 A. Initial femtosecond results for epitaxially-grown chloro-indium phthalocyanine structures, which meet these criteria, are similar to those for the nearly-amorphous film, but indicate an additional polarization-dependent photo-induced absorption within the Q-band.

Photoisomerization in different classes of azobenzene

Abstract: Azobenzene undergoes trans → cisisomerization when irradiated with light tuned to an appropriate wavelength. The reverse cis →transisomerization can be driven by light or occurs thermally in the dark. Azobenzene's photochromatic properties make it an ideal component of numerous molecular devices and functional materials. Despite the abundance of application-driven research, azobenzene photochemistry and the isomerization mechanism remain topics of investigation. Additional substituents on the azobenzene ring system change the spectroscopic properties and isomerization mechanism. This critical review details the studies completed to date on the 3 main classes of azobenzene derivatives. Understanding the differences in photochemistry, which originate from substitution, is imperative in exploiting azobenzene in the desired applications.

Design and synthesis of chromophores and polymers for electro-optic and photorefractive applications

Abstract: The ability of nonlinear optical materials to transmit, process and store information forms the basis of emerging optoelectronic and photonic technologies. Organic chromophore-containing polymers, in which the refractive index can be controlled by light or an electric field, are expected to play an important role.

Photo- and electroactive amorphous molecular materials—molecular design, syntheses, reactions, properties, and applications

Abstract: A new field of organic materials science that deals with amorphous molecular glasses has been opened up. In addition, amorphous molecular materials have constituted a new class of functional organic materials for use in various applications. This article is focused on the recent progress of studies on photo- and electroactive amorphous molecular materials, highlighting photochromic amorphous molecular materials, amorphous molecular resists, and amorphous molecular materials for use in devices such as organic EL devices. The molecular design concepts, syntheses, reactions, molecular and solid-state properties, functions, and device fabrication and performance are described.

Photomodulation of liquid crystal orientations for photonic applications

Abstract: Two types of photomodulation of orientations of liquid crystals (LCs) are reviewed: 1) order–disorder phase transitions of LCs induced by photochemical reactions of photochromic molecules and 2) order–order alignment change of LCs (change in LC directors) induced by photochemical reactions or without photochemical events. Both processes produce a large refractive-index modulation, which forms the basis of a range of photonic applications. Various modes of photomodulation of orientations of LCs with plausible mechanisms and their possible applications in photonics are described.