B. L. Volodin

Bio: B. L. Volodin 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 12, co-authored 28 publications receiving 1529 citations. Previous affiliations of B. L. Volodin include California Institute of Technology.

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.

Infrared Photorefractive Polymers and Their Applications for Imaging

Abstract: Photorefractive polymers with high diffraction efficiency in the visible and near-infrared regions of the electromagnetic spectrum have been developed. These polymers, which have a large dynamic range because of their high orientational birefringence, incorporate a dye designed to have a large dipole moment and a high linear polarizability anisotropy. Such polymers have enabled demonstrations of imaging through scattering media, using a holographic time-gating technique at a wavelength that is compatible with the transparency of biological tissues and with the emission of low-cost semiconductor laser diodes.

A polymeric optical pattern-recognition system for security verification

Abstract: POLYMERS that exhibit the photorefractive effect—a light-induced modulation of refractive index—are emerging as attractive materials for optical devices and processing systems1,2. Here we demonstrate one such application using our recently developed high-efficiency photorefractive polymer2. The polymer provides a nonlinear medium in which real-time all-optical image correlation, and hence pattern recognition, can be accomplished. This forms the basis of an optical security system, whereby documents are encoded with practically invisible phase masks (such masks are difficult to forge), which may then be rapidly screened to verify the authenticity of the documents. The wavelengths at which our optical system operates are compatible with commercial low-power semiconductor laser diodes, and the system can be integrated into a compact device at low cost.

Photorefractive polymer-dispersed liquid crystals

Abstract: We report observation of the photorefractive effect in functionalized polymer-dispersed liquid crystals. The photoconductive properties are provided by the polymer matrix, and the field-dependent refractive-index changes are generated by the dispersed nematic liquid-crystal droplets. A high diffraction efficiency (8%) and a high refractive-index modulation amplitude (Dn = 2 x 10(-3)) are obtained in 53- microm-thick samples with an applied field of 22 V/microm.

Highly efficient photorefractive polymers for dynamic holography

Abstract: The performance of recently developed highly efficient photoref_ ract1ve polyme_rs .base~ on the photoconducting polymer host poly( N-vinylcarbazole) 1s 1nvest1gated, and the use of these materials as recording media in dynamic holography and other applications is evaluated.- A diffraction efficiency 'rJ = 86% (limited only by absorption and reflection losses), a two-beam coupling net gain coefficient r = 200 cm - 1 and light-induced refractive index modulations as high as lin=7X 10-3 are demonstrated. Hologram growth rates of the order of 500 ms are observed with. recording light intensities <10 mW /cm2 , using either lowpower laser diodes (675 nm) or a HeNe laser (633 nm). The materials show good sensitivity in this part of the spectrum. Applications such as dynamic time-average interferometry are demonstrated.

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.

Organic Optoelectronic Materials: Mechanisms and Applications

Abstract: Organic (opto)electronic materials have received considerable attention due to their applications in thin-film-transistors, light-emitting diodes, solar cells, sensors, photorefractive devices, and many others. The technological promises include low cost of these materials and the possibility of their room-temperature deposition from solution on large-area and/or flexible substrates. The article reviews the current understanding of the physical mechanisms that determine the (opto)electronic properties of high-performance organic materials. The focus of the review is on photoinduced processes and on electronic properties important for optoelectronic applications relying on charge carrier photogeneration. Additionally, it highlights the capabilities of various experimental techniques for characterization of these materials, summarizes top-of-the-line device performance, and outlines recent trends in the further development of the field. The properties of materials based both on small molecules and on conjug...

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.