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Diffraction Efficiency (diffraction + efficiency)
Selected AbstractsSyntheses and properties of polyurethanes containing side-chain azobenzene groupsPOLYMER INTERNATIONAL, Issue 5 2003Mi-Ra Kim Abstract Polymers containing azobenzene groups have the characteristic reaction of photo-induced cis,trans isomerism. The study of new materials for optical information storage has prompted making use of these photo-isomerizations. In this study, we report the syntheses and properties of four different polyurethanes (DR-PUns) containing azobenzene groups in the side-chains. The structurally similar polyurethanes (DR-PUns) were synthesized by the polycondensation reaction of Disperse Red 19 (DR 19) and four different diisocyanates in dimethylformamide. By introducing of DR 19 into the polymer, we obtained polymers containing a photochromic group in the side-chain. The weight-average molecular weights of the DR-PUns were in the range 5500,12,900. The Tgs of the DR-PUns range from 119.5,°C to 157.0,°C, depending on the structure of the diisocyanate. Optical properties and solubilities of the polyurethanes were compared. The diffraction efficiencies of films were measured as a function of the reaction time. Typically, the diffraction efficiencies of the DR-PU1 film prepared from toluene 2,4-diisocyanate were observed up to a level of 0.25%. For the DR-PU1 film, the effect of the intensity of the induced laser beam on the diffraction efficiency is also discussed. © 2003 Society of Chemical Industry [source] Effect of reduction/oxidation treatment on blue photorefraction in In:Fe:Cu:LiNbO3 crystalsCRYSTAL RESEARCH AND TECHNOLOGY, Issue 4 2010Suhua Luo Abstract In:Fe:Cu:LiNbO3 crystals with reduced/oxidized treatments were prepared by the Czochralski method. The defect structure was analyzed by the UV-Visible absorption spectra. The blue photorefractive properties, such as the refractive index change, response time, recording sensitivity, dynamic range as well as two-wave coupling gain coefficient, were also investigated at 488 nm wavelength using the two-wave coupling experiment. Comparing the as-grown and oxidized In:Fe:Cu:LiNbO3 crystals, the reduced sample has the highest recording sensitivity and largest dynamic range. Meanwhile, the high diffraction efficiency is still maintained. Experimental results definitely show that reduction treatment is an effective method to improve the blue photorefractive performance of In:Fe:Cu:LiNbO3 crystals. (© 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Growth and photorefractive properties of Mg:Ce:Cu:LiNbO3 crystals grown by Czochralski methodCRYSTAL RESEARCH AND TECHNOLOGY, Issue 8 2006Y. X. Fan Abstract In this paper, photorefractive properties of Mg:Ce:Cu:LiNbO3 crystals were studied. The crystals doped with different concentration of Mg ions have been grown by the Czochralski method. Mg concentrations in grown crystals were analyzed by an inductively coupled plasma optical emission spectrometry (ICP-OE/MS). The crystal structures were analyzed by the X-ray powder diffraction (XRD), ultraviolet-visible (UV-Vis) absorption spectra and infrared (IR) transmitatance spectra. The photorefractive properties of crystals were experimentally studied by using two-beam coupling. In this experiment we determined the writing time, maximum diffraction efficiency and the erasure time of crystals samples with He-Ne laser. The results showed that the dynamic range (M/#), sensitivity (S) and diffraction efficiency (,) were dependent on the Mg doping concentration, and the Mg(4.58mol%):Ce:Cu:LiNbO3 crystal was the most proper holographic recording media material among the six crystals studied in the paper. (© 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Synthesis and photorefractivity of poly[methyl-3-(7-dibenzo[a,g]carbazolyl)-propylsiloxane]JOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 5 2008In Kyu Moon Abstract 7H -Dibenzo[a,g]carbazole-substituted polysiloxane (PSX-[a,g]BCz) has been synthesized by hexachloroplatinate (IV) hydrate polymerization from poly(methylhydrosiloxane) and 7-ally-7H -dibenzo[a,g]carbazole. PSX-[a,g]BCz composite showed large orientational birefringences because of both large dipole moments and high-polarizability anisotropies of P-IP-DC chromophore associated with the effective conjugation along the polyene. The 50-,m thick photorefractive material containing 30 wt % 2-[3-[(E)-2(piperidino)-1-ethenyl]-5,5-dimethyl]-2-cyclohexenyliden]malononitrile showed a diffraction efficiency of 51% at 55 V/,m, which corresponded to a ,n of 3.45 × 10,3. PSX-[a,g]BCz composite shows a fast time constant of 0.42 s at 34 °C and 55 V/,m, which corresponded to the space-charge field of 12 V/,m under 70 V/,m. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 1783,1791, 2008 [source] Actively Q-switched, diode pumped thulium laserLASER PHYSICS LETTERS, Issue 12 2007J.K. Jabczynski Abstract 6 W of output power and near 50% slope efficiency with respect to absorbed pump power was demonstrated in freerunning mode for a short, 40-mm long resonator. The uncoated, with 3.5% dopant of thulium YLF rod of.3× 8 mm size wrapped with indium foil was mounted in copper heat-sink maintaining 293 K temperature of coolant water and inserted in a short, 40-mm long resonator. For pumping the fiber coupled (0.4 mm core diameter) laser diode bar at 792-nm wavelength was deployed. The fused silica acousto-optic modulator with above 80% diffraction efficiency for 25-W power of RF was taken as the Q-switch for such a laser. In the best case of Qswitching mode up to 2-mJ output energy with 20-ns pulse duration corresponding to 100-kW peak power was demonstrated for rep. rate of a few Hz. Emission wavelength was around 1904 nm for both free-running and Q-switching regimes. (© 2007 by Astro Ltd., Published exclusively by WILEY-VCH Verlag GmbH & Co. KGaA) [source] Nanosized-Silica-Reinforced Holographic Polymer-Dispersed Liquid CrystalsMACROMOLECULAR RAPID COMMUNICATIONS, Issue 7 2006Eun Hee Kim Abstract Summary: Nanosized silicas added to holographic polymer-dispersed liquid crystals (HPDLC) provide the resin phase with increased elasticity, dimensional stability, and the high diffraction efficiency of the gratings. On the other hand, nucleation and growth of periodic modulation are delayed, especially with small-sized silica because of the increased viscosity of the resin mixture. Effects of the LC/resin composition and cell gap on the diffraction efficiency have also been studied. AFM image of silica added HPDLC. [source] Effects of solvent, film thickness, and hydrogen bonding on surface-relief gratingsPOLYMER ENGINEERING & SCIENCE, Issue 5 2009Woo-Hyuk Jung This work focuses on the development of a new type of surface-relief grating (SRG) using more effective materials than a typical epoxy-based azopolymer for the recording layer of optical data storage. Thus, aniline-based azopolymers were synthesized by reaction of N,N -diglycidylaniline with aniline (An) followed by diazocoupling with 4-aminobenzonitrile or 4-nitroaniline. Such azopolymers when spin-cast from THF/dioxane showed better diffraction efficiency than those cast from THF alone due to residual dioxane creating a large free volume in the solid state. A second diazocoupling reaction of the diazopolymers initially obtained produced polymers with bis(diazobenzene) substituents which exhibited a higher saturation level of the diffraction efficiency for a thicker than for a thinner film. Azopolymers in which the diazo substituents incorporated hydroxyl groups ortho to the diazo unit were obtained via the reaction of the diglycidyl ether of bisphenol-A with aniline or 3-hydroxyaniline followed by coupling with diazotised hydroxynitroaminobenzene. These hydroxy groups, presumably as a result of their H-bonding to the diazo-N, effectively prevented the photoisomerization of the chromophores, so that the polymers showed no SRG at a normal laser intensity of 100 mW/cm2. Polyurethane-based azopolymers, synthesized with toluene-2,4-diisocyanate and disperse orange 17 containing no hydroxyl groups in the main chains, showed better diffraction efficiency than the other azopolymers with nitro group substituents. POLYM. ENG. SCI., 2009. © 2009 Society of Plastics Engineers [source] Syntheses and properties of polyurethanes containing side-chain azobenzene groupsPOLYMER INTERNATIONAL, Issue 5 2003Mi-Ra Kim Abstract Polymers containing azobenzene groups have the characteristic reaction of photo-induced cis,trans isomerism. The study of new materials for optical information storage has prompted making use of these photo-isomerizations. In this study, we report the syntheses and properties of four different polyurethanes (DR-PUns) containing azobenzene groups in the side-chains. The structurally similar polyurethanes (DR-PUns) were synthesized by the polycondensation reaction of Disperse Red 19 (DR 19) and four different diisocyanates in dimethylformamide. By introducing of DR 19 into the polymer, we obtained polymers containing a photochromic group in the side-chain. The weight-average molecular weights of the DR-PUns were in the range 5500,12,900. The Tgs of the DR-PUns range from 119.5,°C to 157.0,°C, depending on the structure of the diisocyanate. Optical properties and solubilities of the polyurethanes were compared. The diffraction efficiencies of films were measured as a function of the reaction time. Typically, the diffraction efficiencies of the DR-PU1 film prepared from toluene 2,4-diisocyanate were observed up to a level of 0.25%. For the DR-PU1 film, the effect of the intensity of the induced laser beam on the diffraction efficiency is also discussed. © 2003 Society of Chemical Industry [source] Effects of surfactant and molecular weight of polyol on grating formation and switching of holographic PDLCPOLYMERS FOR ADVANCED TECHNOLOGIES, Issue 11 2008S. S. Shim Abstract The interposition of surfactants between polymer and liquid crystal (LC) droplets was theoretically predicted by the positive spreading coefficient (0,<,,31) and utilized to interpret the morphology, grating formation kinetics, diffraction efficiency, and switching of the holographic polymer dispersed liquid crystal (HPDLC), prepared from various types (octanoic acid, poly oxyethylene octyl phenyl ether, and perfluoro-1-butanesulfonyl fluoride) and amounts (0,9 wt%) of surfactant and molecular weights of polyol (PPG). Regardless of the surfactant type, diffraction efficiency increased with the addition and increasing amount of surfactant, a tendency consistent with increasing value of spreading coefficient, which is determined by the formulations of grating formation. In contrast, diffraction efficiency showed a maximum with the polypropylene glycol (PPG) molecular weight. Surfactant effectively reduced the anchoring energy and electrically drove the film which otherwise was not driven. Overall, surfactant with greater ,31 gave smaller droplet, greater diffraction efficiency, driving voltage, contrast ratio, and smaller response time. Copyright © 2008 John Wiley & Sons, Ltd. [source] Surfactant Effects on Morphology and Switching of Holographic PDLCs Based on Polyurethane Acrylates,CHEMPHYSCHEM, Issue 1 2007Ju Yeon Woo Abstract Effects of octanoic acid (OA) on the morphology, diffraction efficiency, and electro-optic properties of the transmission mode of holographic polymer,dispersed liquid crystals (HPDLC) are studied. Droplet size decreases with increasing OA content (0,9,%), and this leads to a monotonic increase in off-state diffraction with increasing OA content. However, on-state diffraction decreases with increasing applied voltage and shows a minimum at 6,% OA, for which minimum switching voltage (5 V,,m,1) and maximum contrast ratio (10) are obtained. Rise time and decay time decrease with increasing OA content. Interposition of OA between polymer and LC droplet is theoretically predicted by the spreading coefficient (,>0) calculated on the basis of the solubility parameter, while the coalescence behavior of droplets is described by a dimensionless group () called coalescence number. [source] | |||||||||||||