Photorefractive crystals play an increasingly important role in optical information processing. Some of these crystals have been used in a variety of optical computing applications. The photorefractive response time is a critical issue because it directly determines the processing speed of the devices. Crystals that are widely used at present, such as BaTiO/sub 3/, LiNbO/sub 3/, and SBN, etc., are relatively slow when the light intensity is 1 W/cm/sup 2/. Semiconductor crystals such as GaAs and GaP have a higher speed but suffer from small coupling constants. For high processing speed, KNbO/sub 3/ has the best promise because it has the highest figure of merit among the oxide photorefractive crystals. Volt et. al studied the photorefractive response time of KNbO/sub 3/:Fe. They found that reduction of the crystal could decrease the response time by several orders of magnitude. However, such KNbO/sub 3/ crystals often become optically inhomogeneous after reduction. In this paper, we report our investigation of the transient photorefractive response of KNbO/sub 3/:Rb/sup +/ crystals, which exhibit a fast response time while maintaining a significant gain and good optical homogeneity for information processing applications.< >
The confined self-assembly of asymmetric diblock copolymer polystyrene-block-poly(methyl methacrylate) (PS-b-PMMA) within an array of silica nanobowls prepared using a colloidal spheres templating technique is investigated. By manipulation of the nanobowl size, block copolymer (BCP) thickness, and interfacial interaction, a rich variety of ordered BCP nanostructures not accessible in the bulk system or under other confinements are obtained, resulting in hierarchically ordered nanostructures.
KNbO 3 crystals doped with Co have been grown by the Kyropoulos method. The density of Co ions in the crystal is about 100 parts in 10 6 . The inhomogeneity of refractive index Δ n < 10 −5 /cm. The ordinary dimensions of single-domain KNbO 3 :Co crystals are about 10 × 10 × 10 mm 3 . Photorefractlve properties of KNbO 3 :Co have been compared with those of KNbO 3 :Fe. It has been found that the photorefractive diffraction efficiency of KNbO 3 :Co crystal without being reduced is one order of magnitude larger than that of reduced KNbO 3 :Fe crystal. The two wave coupling intensity distribution with the change of entering direction of the laser beam has been measured, and the distribution curve has been given. Other photorefractive experiments are being carryied out, and the results will be reported.
Here we report the design and preparation of a novel self-reporting sensor for cholic acid, an important biological compound produced in hepatocytes. Traditional detection methods of cholic acid are mostly dependent on analytical equipment, and are either time-consuming or require a derivatization process. In this work, a new approach based on molecularly imprinted photonic hydrogels (IPHs) is described, by which direct, sensitive and label-free detection of cholic acid can be achieved without any derivatization treatment and expensive instruments. The unique 3D ordered porous hydrogels that reveal optical changes in responsive to cholic acid concentration were prepared by combining colloidal crystal templating with the molecular imprinting technique. Due to their special hierarchical porous structure, which consists of 3D-ordered interconnected macroporous arrays with nanocavities derived from molecular imprinting, the formed photonic hydrogels allow rapid and ultrasensitive detection of the target analyte. The interconnected macropores are favorable for the rapid transport of the analyte in the hydrogel, while the inherent high affinity of nanocavities distributed in thin hydrogel walls allows IPHs to recognize the analyte with high specificity.
An entry from the Cambridge Structural Database, the world’s repository for small molecule crystal structures. The entry contains experimental data from a crystal diffraction study. The deposited dataset for this entry is freely available from the CCDC and typically includes 3D coordinates, cell parameters, space group, experimental conditions and quality measures.
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