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961.
Jacquin O. Benyattou T. Desieres Y. Orobtchouk R. Cachard A. Benech P. 《Optical and Quantum Electronics》2000,32(6-8):935-945
The concept of the photonic band gap (PBG) structures stems from ideas of Yablonovitch. The idea is to design components so that they affect the properties of photons, in much the same way that ordinary semiconductor crystals affect the properties of electrons. In fact, the PBG structures forbid propagation of photons for a particular range of energy. They can be used to realise optical filters with large stop band and sharp transmission resonance. In the guided PBG structures, the existence of diffractive effects in the vertical dimension could limit the quality factor of such filters. In this paper, we have investigated the origin of diffraction losses in one-dimensional guided PGB structures using 2D and 3D numerical tools. We propose an analytical approach based on Bragg diffraction relation to explain these losses phenomenon. From this approach, the influence of some design parameters on the electromagnetic behaviour and the spectral response of PBG resonators will be explained. 相似文献
962.
Y. -M. Yu S. Nam J. -K. Rhee Byungsung O K. -S. Lee Y. D. Choi 《Journal of Crystal Growth》2000,210(4):521-526
ZnS1−xTex epilayers were grown on GaAs(1 0 0) substrates by hot-wall epitaxy in a wide range of Te composition. The Te composition was determined by Rutherford backscattering spectrometry and the lattice constant was measured by double-crystal rocking curve. It was found that the lattice of the epilayer matches well with that of the substrate at x=0.37 as expected by Vegard's rule, and the energy gap was also determined as a function of Te composition by spectrophotometer. It showed that a quadratic relation with the composition: Eg(x)=3.71−5.27x+3.83x2. Photoluminescence characteristics were also studied. 相似文献
963.
利用快速平面波展开法研究了两种长方晶格光子晶体,发现它们在高频区都存在大带
隙,经参数优化,原胞结构为“工”字形的光子晶体,最大绝对禁带宽度Δω为0. 1393ωe (ωe =2πc / a, a为晶格常数, c为光速) ,绝对禁带中心频率ωmid为1. 7368ωe ,Δω/ωmid = 8. 02%;原胞结构为“王”字形的光子晶体,最大绝对禁带宽度Δω为0. 1544ωe ,绝对禁带中心频率ωmid为1. 5854ωe ,Δω/ωmid = 9. 74%。 相似文献
964.
965.
The temperature dependent band gap energy of Cu2ZnSnS4 thin film was studied in the temperature range of 77-410 K. Various relevant parameters, which explain the temperature variation of the fundamental band gap, have been calculated using empirical and semi-empirical models. Amongst the models evaluated, the Varshni and Pässler models show the best agreement with experimental data in the middle temperature range. However, the Bose-Einstein model fits reasonably well over the entire temperature range evaluated. The calculated fitting parameters are in good agreement with the estimated value of the Debye temperature calculated using the Madelung-Einstein approximation and the Hailing method. 相似文献
966.
The global view of firewall policy conflict is important for administrators to optimize the policy.It has been lack of appropriate firewall policy global conflict analysis,existing methods focus on local conflict detection.We research the global conflict detection algorithm in this paper.We presented a semantic model that captures more complete classifications of the policy using knowledge concept in rough set.Based on this model,we presented the global conflict formal model,and represent it with OBDD(Ordered Binary Decision Diagram).Then we developed GFPCDA(Global Firewall Policy Conflict Detection Algorithm) algorithm to detect global conflict.In experiment,we evaluated the usability of our semantic model by eliminating the false positives and false negatives caused by incomplete policy semantic model,of a classical algorithm.We compared this algorithm with GFPCDA algorithm.The results show that GFPCDA detects conflicts more precisely and independently,and has better performance. 相似文献
967.
Mallari A. Naik Satish Patil 《Journal of polymer science. Part A, Polymer chemistry》2013,51(20):4241-4260
The present highlight discusses major work in the synthesis of low bandgap diketopyrrolopyrrole ( DPP )‐based polymers with donor–acceptor–donor ( D–A–D ) approach and their application in organic electronics. It examines the past and recent significant advances which have led to development of low bandgap DPP ‐based materials with phenyl and thiophene as donors. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2013, 51, 4241–4260 相似文献
968.
Ching‐Chih Chang Chih‐Ping Chen Ho‐Hsiu Chou Chuang‐Yi Liao Shu‐Hua Chan Chien‐Hong Cheng 《Journal of polymer science. Part A, Polymer chemistry》2013,51(21):4550-4557
Low‐band gap selenophene‐based polymers were synthesized. Their optoelectronic and photovoltaic properties and space‐charge limited currents were compared with those of the related thiophene‐based polymers. The band gaps of the Se‐based derivatives were approximately 0.05–0.12 eV lower than those of their thiophene counterparts. Organic photovoltaic (OPV) devices based on the blends of these polymers and 1‐(3‐methoxycarbonyl)propyl‐1‐phenyl‐[6,6]‐C71 (PC71BM) were fabricated, and the maximum power conversion efficiency of the OPV device based on PSPSBT and PC71BM was 3.1%—with a short‐circuit current density (Jsc) of 9.3 mA cm?2, an open‐circuit voltage (Voc) of 0.79 V, and a fill factor of 0.42—under AM 1.5 G illumination (100 mW cm?2). © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2013 , 51, 4550–4557 相似文献
969.
Based on the transfer matrix method (TMM) and Bloch theory, the interaction of elastic waves (normal incidence) with 1D phononic crystal had been studied. The transfer matrix method was obtained for both longitudinal and transverse waves by applying the continuity conditions between the consecutive unit cells. Dispersion relations are calculated and plotted for both binary and ternary structures. Also we have investigated the corresponding effects on the band gaps values for the two types of phononic crystals. Furthermore, it can be observed that the complete band gaps are located in the common frequency stop-band regions. Numerical simulations are performed to investigate the effect of different thickness ratios inside each unit cell on the band gap values, as well as unit cells thickness on the central band gap frequency. These phononic band gap materials can be used as a filter for elastic waves at different frequencies values. 相似文献
970.
在分析计算金属光子晶体的正三角形晶格TE模式的色散特性、全局带隙分布图的基础上,针对TE04模光子晶体谐振腔中仍有较多的模式竞争且金属柱半径较小的问题,结合模式分布特点图,通过优化和选择工作点的位置,将TE04中的竞争模从5种减少为2种,大幅度降低了TE04工作模式中的模式竞争,并且增加了晶格常数和金属柱半径,使之能够承受更大的热损耗,有利于提高腔体功率容量。仿真验证了数值计算的正确性并得出了完整的TE04场分布。 相似文献