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951.
Bjrn Kemper Stephan Stürwald Christian Remmersmann Patrik Langehanenberg Gert von Bally 《Optics and Lasers in Engineering》2008,46(7):499-507
Partial coherent light sources open up prospects for phase noise reduction in digital holographically reconstructed phase distributions by suppressing multiple reflections in the experimental setup. Thus, light emitting diodes (LEDs) are investigated for application in digital holographic microscopy. First, the spectral properties and the resulting coherence length of an LED are characterised. In addition, an analysis of dispersion effects and their influence on the hologram formation is carried out. The coherence length of LEDs in the range of a few micrometers restricts the maximum interference fringe number in off-axis holography for spatial phase shifting. Thus, the application of temporal phase-shifting-based digital holographic reconstruction techniques is compared to spatial phase-shifting-based methods. It is demonstrated that LEDs are applicable for digital holographic microscopy in connection with both spatial and temporal phase-shifting-based techniques for reduction of noise in comparison to a laser-light-based experimental setup. 相似文献
952.
This paper reports the determination of electrical equivalent circuit of ON/OFF modulator in non-radiative dielectric (NRD)
guide configurations at Ka-band. Schottky barrier mixer diode is used to realize this modulator and its characteristics are
determined experimentally using vector network analyzer. Full wave FEM simulator HFSS is used to determine an equivalent circuit
for the mounted diode and modulator in ON and OFF states. This equivalent circuit is used to qualitatively explain the experimental
characteristics of modulator.
相似文献
953.
Jonghee Lee Hoon‐Je Cho Nam Sung Cho Do‐Hoon Hwang Jong‐Min Kang Eunhee Lim Jeong‐Ik Lee Hong‐Ku Shim 《Journal of polymer science. Part A, Polymer chemistry》2006,44(9):2943-2954
Two novel organic–inorganic hybrid polyfluorene derivatives, poly{(9,9′‐dioctyl‐2,7‐fluorene)‐co‐(9,9′‐di‐POSS‐2,7‐fluorene)‐co‐[2,5‐bis(octyloxy)‐1,4‐phenylene]} (PFDOPPOSS) and poly{(9,9′‐dioctyl‐2,7‐fluorene)‐co‐(9,9′‐di‐POSS‐2,7‐fluorene)‐co‐bithiophene} (PFT2POSS), were synthesized by the Pd‐catalyzed Suzuki reaction of polyhedral oligomeric silsesquioxane (POSS) appended fluorene, dioctyl phenylene, and bithiophene moieties. The synthesized polymers were characterized with 1H NMR spectroscopy and elemental analysis. Photoluminescence (PL) studies showed that the incorporation of the POSS pendant into the polyfluorene derivatives significantly enhanced the fluorescence quantum yields of the polymer films, likely via a reduction in the degree of interchain interaction as well as keto formation. Additionally, the blue‐light‐emitting polyfluorene derivative PFDOPPOSS showed high thermal color stability in PL. Moreover, single‐layer light‐emitting diode devices of an indium tin oxide/poly(3,4‐ethylene dioxythiophene):poly(styrene sulfonate)/polymer/Ca/Al configuration fabricated with PFDOPPOSS and PFT2POSS showed much improved brightness, maximum luminescence intensity, and quantum efficiency in comparison with devices fabricated with the corresponding pristine polymers PFDOP and PFT2. In particular, the maximum external quantum efficiency of PFT2POSS was 0.13%, which was twice that of PFT2 (0.06%), and the maximum current efficiency of PFT2POSS was 0.38 cd/A, which again was twice that of PFT2 (0.19 cd/A). © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 2943–2954, 2006 相似文献
954.
955.
Diffusion, solubility, and permebility coefficients were measured for He, Co2, Ar, and CH4 in polybutadiene (PB) and in polybutadiene reacted in the solid state to various extents with aqueous bromine. Analysis of the sorption curves and X-ray emission spectra showed that the bromination created a heterogeneous membrane with an outer brominated skin and an unreacted core. At relatively low extent of bromination, the diffusion and permeability coefficients for CO2, Ar, and CH4 decreased by two orders of magnitude, while the transport coefficients for He were virtually unchanged. The permeability coefficients for CO2, Ar, and CH4 became immeasurably small after about 3% bromination. The ideal separation factor for gas pairs with different molecular size increased with bromination, suggesting applications in gas separation processes. © 1993 John Wiley & Sons, Inc. 相似文献
956.
The oscillation frequency shift ratio (OFSR) of a three-cavity coupled laser diode, which is caused by refractive index changes due to current modulation and temperature variation, has been investigated. It is found that the OFSR is significantly reduced by using a laser with an AR coated facet and a high external-mirror reflectivity, in addition to large external cavity lengths. Also, compared with an external cavity laser, the three-cavity laser has a smaller OFSR provided that the external cavities' reflectivities r0 and r3, are not identical (that is, r3 > r0). The analysis indicates that the structural parameters affect the OFSR of the three-cavity laser, which was shown to have a high longitudinal mode discrimination1. 相似文献
957.
Kun‐Ming Yeh Chih‐Cheng Lee Yun Chen 《Journal of polymer science. Part A, Polymer chemistry》2008,46(15):5180-5193
Vinyl copolymers (PCOn), containing pendant carbazole and aromatic 1,3,4‐oxadiazole attached with dodecyloxy group, were prepared from their corresponding precursor poly(9‐vinyl carbazole‐co‐4‐vinylbenzyl chloride) (PCBn) by the Williamson condensation (n: mole% of 4‐vinylbenzyl chloride). These copolymers were used as host materials for green phosphorescent light‐emitting diodes after blending 4 wt % of Ir(ppy)3. PL spectra of the PCOn films showed the formation of excimer or exciplex. The phosphorescent EL devices were fabricated with a configuration of ITO/PEDOT:PSS/host copolymers:Ir(ppy)3/BCP/Ca/Al. The PL and EL spectra of the blends [PCOn:Ir(ppy)3] revealed dominant green emission at 517 nm attributed to Ir(ppy)3 due to efficient energy transfer from the host to Ir(ppy)3. Efficient green phosphorescent OLEDs was obtained when employing copolymer PCO16 as the host and Ir(ppy)3 as the guest. The maximal luminance efficiency and the maximal luminance of this device were 17.9 cd/A and 19,903 cd/m2, respectively. After doped with Ir(ppy)3, the morphology of the films, both controlled PCO20 and PCO20 with attached dodecyloxy groups, were investigated by tapping‐mode AFM and FE‐SEM. The film of PCO20 exhibited uniform, featureless image and showed much better device performance than PCO20, which have been attributed to good compatibility of PCO20 with Ir(ppy)3. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 5180–5193, 2008 相似文献
958.
Sung‐Chul Kim Seung‐Min Park Jin Soo Park Seung‐Joon Lee Sung‐Ho Jin Yeong‐Soon Gal Jae Wook Lee 《Journal of polymer science. Part A, Polymer chemistry》2008,46(3):1098-1110
Two PPV‐based bipolar polymers containing 1,3,4‐oxadiazole pendant groups were synthesized via the Gilch polymerization reaction for use in light‐emitting diodes (LEDs). The resulting polymers were characterized using 1H and 13C NMR, elemental analysis, DSC, and TGA. These polymers were found to be soluble in common organic solvents and are easily spin‐coated onto glass substrates, producing high optical quality thin films without defects. The electro‐optical properties of ITO/PEDOT/polymer/Al devices based on these polymers were investigated using UV‐visible, PL, and EL spectroscopy. The turn‐on voltages of the OC1Oxa‐PPV and OC10Oxa‐PPV devices were found to be 8.0 V. The maximum brightness and luminescence efficiency of the OC1Oxa‐PPV device were found to be 544 cd/m2 at 19 V and 0.15 cd/A, respectively. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 1098–1110, 2008 相似文献
959.
Panagiotis D. Vellis John A. Mikroyannidis Min Ju Cho Dong Hoon Choi 《Journal of polymer science. Part A, Polymer chemistry》2008,46(16):5592-5603
Two new soluble alternating carbazolevinylene‐based polymers POXD and PTPA as well as the corresponding model compounds MOXD and MTPA were synthesized by Heck coupling. POXD and MOXD contained 2,5‐diphenyloxadiazole segments, while PTPA and MTPA contained triphenylamine segments. All samples displayed high thermal stability. The polymers had higher glass transition temperature (Tg) than their corresponding model compounds. The samples showed absorption maximum at 364–403 nm with optical band gap of 2.62–2.82 eV. They emitted blue‐green light with photoluminescence (PL) emission maximum at 450–501 nm and PL quantum yields in THF solution of 0.15–0.36. The absorption and the PL emission maxima of PTPA and MTPA were blue‐shifted as compared to those of POXD and MOXD . The electroluminescence (EL) spectra of multilayered devices made using four materials exhibited bluish green emissions, which is well consistent with PL spectra. The EL devices made using poly(vinyl carbazole) doped with MOXD and MTPA as emitting materials showed luminances of 12.1 and 4.8 cd m?2. POXD and PTPA exhibited 25.4, and 96.3 cd m?2, respectively. The polymer containing the corresponding molecules in the repeating group showed much higher device performances. Additionally, POXD and MOXD exhibited better stability of external quantum efficiency (EQE) and luminous efficiency with current density resulting from enhancing the electron transporting properties. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 5592–5603, 2008 相似文献
960.
Roberto Grisorio Claudia Piliego Paola Fini Pinalysa Cosma Piero Mastrorilli Giuseppe Gigli Gian Paolo Suranna Cosimo Francesco Nobile 《Journal of polymer science. Part A, Polymer chemistry》2008,46(18):6051-6063
The synthesis of new random poly(2,7‐fluorenylene‐vinylene)s was achieved by a Suzuki–Heck cascade polymerization reaction. The poly(fluorenylene‐vinylene) base structure was modified by the regio‐random incorporation of 1‐cyano‐2,5‐phenylene as electron withdrawing unit ( CN‐PFV1 ) and its properties were compared with terpolymers also embodying 1,4‐dioctyloxy‐2,5‐phenylene ( CN‐PFV2 ) or 3,6‐N‐octylcarbazole ( CN‐PFV3 ) as electron‐donating moieties. Thermal analysis revealed a high thermal stability (Td > 389 °C) and the absence of glass transitions for all polymers. Cyclic voltammetry indicated a high electron affinity of the materials (2.96–3.21 eV) attributed to the presence of the cyano‐containing comonomer. In dilute solutions, the copolymers showed a broad green fluorescence with quantum yields ranging from 0.42 to 0.79, while in the solid state, a relatively narrow emission centered at ~ 560 nm, governed by the low‐energy segments within the π‐conjugated backbone, was observed. The electroluminescence properties of the materials were tested in OLED devices of ITO/PEDOT‐PSS/ CN‐PFV1‐3 /Ca/Al or ITO/PEDOT‐PSS/ CN‐PFV1‐3 /Alq3/Ca/Al configurations, showing a bright green‐yellow emission that, in the case of CN‐PFV2 , reached 1403 cd/m2 with efficiencies as high as 0.13 cd/A. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 6051–6063, 2008 相似文献