Surface characteristics of SiO2-TiO2 strip fabricated by laser direct writing

SiO2-TiO2 sol-gel films are deposited on SiO2/Si by dip-coating technique. The SiO2-TiO2 strips are fabricated by laser direct writing using all ytterbium fiber laser and followed by chemical etching. Surface structures, morphologies and roughness of the films and strips are characterized. The experimental results demonstrate that the SiO2-TiO2 sol-gel film is loose in Structure and a shrinkage concave groove forms if the film is irradiated by laser beam. The surface roughness of both non-irradiated and laser irradiated areas increases with the chemical etching time. But the roughness of laser irradiated area increases more than that of non-irradiated area under the same etching time. After being etched for 28 s, the surface roughness value of the laser irradiated area increases from 0.3 nm to 3.1 nm.

Design and Fabrication of AlGaN-Based Resonant-Cavity-Enhanced p-i-n UV PDs

AlGaN-based resonant-cavity-enhanced (RCE) p-i-n photodetectors (PDs) for operating at the wavelength of 330 nm were designed and fabricated. A 20.5-pair AlN/Al0.3Ga0.7N distributed Bragg reflector (DBR) was used as the back mirror and a 3-pair AlN/Al0.3Ga0.7N DBR as the front one. In the cavity is a p-GaN/i-GaN/n-Al0.3Ga0.7N structure. The optical absorption of the RCE PD structure is at most 59.8% deduced from reflectance measurement. Selectively enhanced by the cavity effect, a response peak of 0.128 A/W at 330 nm with a half-peak breadth of 5.5 nm was obtained under zero bias. The peak wavelength shifted 15 nm with the incident angle of light increasing from 0 degrees to 60 degrees.

Integratable and High Speed Complex-Coupled MQW-DFB Lasers Fabricated on Semi-Insulating Substrates

A novel integratable and high speed InGaAsP multi-quantum well (MQW) complex-coupled distributed feedback (DFB) laser is successfully fabricated on a semi-insulating substrate. The fabricated ridge DFB laser exhibits a threshold current of 26 mA, a slope efficiency of 0.14 W.A(-1) and a side mode suppression ratio of 40 dB together with a 3 dB bandwidth of more than 8 GHz. The device is suitable for 10 Gbit/s optical fiber communication.

Novel triplexing-filter design using silica-based direction coupler and an arrayed waveguide grating

A new triplexing filter based on a silica direction coupler and an arrayed waveguide grating is presented. Using a combination of a direction coupler and an arrayed waveguide grating, a 1310-nm channel is multiplexed and 1490- and 1550-nm channels are demultiplexed for fiber-to-the-home. The direction coupler is used to coarsely separate the 1310-nm channel from the 1490- and 1550-nm channels. Subsequently, an arrayed waveguide grating is used to demultiplex the 1490- from 1550-nm channel. The simulated spectra show the 1-dB bandwidth of 110 nm for the 1310-nm channel and 20 and 20.5 nm for the 1490- and 1550-nm channels. The insertion loss is only 0.15 dB for 1310 nm and 5 dB for 1490 and 1550 nm. The crosstalk between the 1490- and 1550-nm channels was less than -35 dB. (C) 2009 Society of Photo-Optical Instrumentation Engineers. [DOI 10.1117/1.3065508]

All-optical continuously tunable delay with a high linear-chirp-rate fiber Bragg grating based on four-wave mixing in a highly-nonlinear photonic crystal fiber

A scheme for hi-fi all-optical continuously tunable delay is proposed. The signal wavelength is converted to a desired idler wavelength and converted back after being delayed by a high linear-chirp-rate (HLCR) fiber Bragg grating (FBG) based on four-wave mixing (FWM) in a highly-nonlinear photonic crystal fiber (HN-PCF). In our experiment, 400 ps (more than 8 full width of half maximum, FWHM) tunable delay is achieved for a 10 GHz clock pulse with relative pulse width broaden ratio (RPWBR) of 2.08%. The power penalty is only 0.3 dB at 10(-9) BER for a 10 Gb/s 2(31)-1 pseudo random bit sequence (PRBS) data. (c) 2009 Elsevier B.V. All rights reserved.

Energy of a polaron in a wurtzite nitride finite parabolic quantum well

The effects of electron-phonon interaction oil energy levels of a. polaron in a wurtzite nitride finite parabolic quantum well (PQW) are studied by using a modified Lee-Low-Pines variational method. The ground state, first excited state, and transition energy of the polaron in the GaN/Al0.3Ga0.7N wurtzite PQW are calculated by taking account of the influence of confined LO(TO)-like phonon modes and the half-space LO(TO)-like phonon modes and considering the anisotropy of all kinds of phonon modes. The numerical results are given and discussed. The results show that the electron phonon interaction strongly affects the energy levels of the polaron, and the contributions from phonons to the energy of a polaron hi a wurtzite nitride PQW are greater than that in all AlGaAs PQW. This indicates that the electron-phonon interaction in a wurtzite nitride PQW is not negligible.

Steady and transient optical properties of cubic InGaN epilayers

Photoluminescence (PL) and time-resolved PI, were employed to study the steady and transient optical properties of cubic InxGa1-xN epilayers grown by MBE. The results suggest that the PL transitions in InGaN epilayers are mainly from localized exciton states. The localization energies are estimated to be 60 meV, independent of In composition. The PL decay is characterized by a hi-exponential dependence. The fast process (50 ps at 12K) is related to the fast relaxation of excitons, while a slower contribution (200-270 ps at 12K) is attributed to the decay process of localized excitons.

High speed silicon optical switches based on carrier depletion - art. no. 67812D

The novel design of a silicon optical switch on the mechanism of a reverse p-n junction is proposed. The figuration of contact regions at slab waveguides and the ion implantation technology for creation of junctions are employed in the new design. The two-layer rib structure is helpful for reduction of optical absorption losses induced by metal and heavily-doped contact. And more, simulation results show that the index modulation efficiency of Mach-Zehnder interferometer enhances as the concentrations of dopants in junctions increase, while the trade-off of absorption loss is less than 3 dB/mu m. The phase shift reaches about 5 x 10(-4) pi/mu m at a reverse bias of 10V with the response time of about 0.2ns. The preliminary experimental results are presented. The frequency bandwidth of modulation operation can arrive in the range of GHz. However, heavily-doped contacts have an important effect on pulse response of these switches. While the contact region is not heavily-doped, that means metal electrodes have schottky contacts with p-n junctions, the operation bandwidth of the switch is limited to about 1GHz. For faster response, the heavily-doped contacts must be considered in the design.

Optical properties of Mn+ doped GaAs

The above work was supported by the national Basic Research Program of China (2006cb604904, 2006cb604908), the hi-tech R & D program of China (2006aa03z0408, 2006aa03z0404), the scientific research Fund of Central South University of Forstry and Technology.

后弯管波力发电浮标模型性能试验研究

为改进后弯管波力发电浮标的性能，对多种模型进行了新一轮试验研究。测定了它们的气室平均输出气流功率随波周期的变化曲线NA－T；试验了不同质量对性能的影响；测出了不同喷咀比ε的波高比Hi／Ho、压力比ΔPi／Ho和波能转换效率ηA。确定了最佳浮体——前方后园浮室后伸型后弯管浮体的尺寸、质量和性能参数。

基于核酸特殊结构的分子识别及核酸相关纳米结构的设计应用

核酸为生命的最基本物质之一，是生物体遗传信息的携带者，在生长、遗传、变异等一系列重大生命现象中起决定性的作用。以核酸作为新药设计的靶分子，越来越受到人们的广泛重视。然而，不像其它靶分子如蛋白质、受体等具有特定的结构和功能，核酸结构在很多情况下是同源的，而且联系到很多人体正常的生理功能；能够与核酸结合的药物又往往不具有序列选择性，这就带来明显的毒副作用。因此，寻找和发现一些与疾病相关的核酸的特殊结构，并筛选对其有特异性结合能力的小分子，是以核酸为靶的药物研究的一个重要课题。 近年来，随着纳米科学技术的兴起，以核酸作为纳米体系的结构材料开始受到人们的广泛关注。作为一类特殊的线性高分子，核酸具有化学性质稳定，结构丰富且可控，良好的刚性和柔性，精确识别，高度生物相容性，合成方便等诸多优点，是一类优良的结构材料。目前核酸相关的纳米组装结构和器件研究还处于起步阶段，但是已经呈现出良好的发展前景。 本论文主要针对核酸特殊结构的分子识别及核酸相关功能纳米结构的设计这两方面展开了研究，全文由以下两大部分组成： 第一部分通过光谱学和生物化学等手段，研究了小分子对不同核酸结构的识别作用。借助于竞争平衡透析技术，发现一类恶嗪染料(oxazine dyes)能够与多种结构核酸结合。热变性及光谱实验结果表明，oxazine染料能够诱导杂合体三链核酸poly(rA):2poly(dT)的形成，并强烈地稳定其结构，其中以cresyl violet作用最强，是迄今发现的化合物中最强的。进一步研究发现，此类化合物以嵌插方式与杂合体三链核酸结合。RNase H酶切实验表明，杂合体三链核酸的形成能够强烈地抑制RNase H核酸酶的活性。研究了oxazine-170与三链核酸poly(dA):2poly(dT)及poly(rA):2poly(rU)的相互作用，发现oxazine-170能够强烈稳定三链DNA poly(dA):2poly(dT)的结构，而对相应双链DNA不具稳定作用；对三链RNA poly(rA):2poly(rU)及相应的双链RNA都有一定稳定作用，但作用不强。进一步研究发现，oxazine-170能够以两种结合方式与核酸结合：嵌插方式和外部静电堆积作用。研究了oxazine-170及cresyl violet与单链核酸的相互作用。研究发现oxazine-170能够序列特异性地与单链核酸poly(rA) 结合，CD光谱及AFM研究发现oxazine-170诱导poly(rA)形成新的二级结构。UV光谱、FL光谱及RLS研究发现poly(rA)促使oxazine 170形成H-aggregate，并以poly(rA)为模板自组装。而cresyl violet能够与单链核酸poly(rA)及poly(dA)结合，且采用不同的结合方式： cresyl violet能够与oxazine-170 类似地以poly(rA)为模板自组装；以嵌插方式与poly(dA)结合，并诱导其单链碱基堆积方式的改变。通过以上实验结果，我们进一步揭示了oxazine染料作为肿瘤细胞染色及光动力学治疗试剂的结构基础，对进一步设计、合成更加高效的抗肿瘤药物具有一定的指导意义。 第二部分中，我们尝试设计了几种基于核酸的纳米结构功能体系，并讨论了其相关应用。利用有机小分子coralyne能够诱导聚腺嘌呤序列反平行双链结构的形成，实现了一类新型的小分子诱导的纳米金组装结构。并以(dA)16功能化的金纳米粒子作为新型纳米探针，发展了一种简单的筛选单链核酸聚腺嘌呤序列结合分子的筛选方法。利用核酸限制性内切酶酶切位点回文序列的结构特点，设计了一种以DNA功能化的金纳米粒子组装体为酶切底物的比较通用的核酸限制性内切酶活力检测方法，并进一步用于甲基化酶活性检测及其抑制剂的筛选。基于单链DNA富胞嘧啶i-motif结构在不同pH值条件下的形成与解离，设计了一类质子驱动的DNA分子镊子，与基于链交换反应的DNA分子镊子相比，该体系更加简单，工作效率更高。随后，我们又通过合理设计，得到了两种分别能够结合与释放DNA和蛋白的分子镊子，为其应用做了一些探索。

天花粉蛋白抗HIV-1构效关系研究及机制探讨

天花粉蛋白（Trichosanthin，TCS）是从葫芦科植物括楼（TrichosanthesKiriloii）球根中提取的一种由247个氨基酸组成的I型核糖体失活蛋白（RibosomeInactivatingProtein，RIP）。TCS具有广谱的生物学和药学活性，包括抗肿瘤、免疫抑制、中期引产以及抗病毒活性，TCS还具有抗白血病和淋巴瘤的作用。TCS能够抑制HI卜1在急性感染的T淋巴细胞和慢性感染的巨噬细胞中的复制。TCS抗HIV的机制还不清楚，一般认为与R1（RibosolneInactivating）活性有关。TCS的毒副作用限制了它在抗HIV／AIDS临床上的进一步应用。人们期望通过改造或修饰，在保留TCS抗HIV活性的同时，降低其神经毒副作用及所引起的变态反应。因此，研究TCS的抗HIV-1作用机制及构效关系，有利于拓宽TCS的临床应用适应症，也对RIP类化合物基础研究和应用研究具有重要的指导作用。本论文在实验室己有研究工作的基础上，对TCS抗HIV-1作用、机制及构效关系进一步研究。首先，采用MTT比色法检侧TcS对人T淋巴细胞系C8166、HIV-1慢性感染细胞系H9／HIV-1IIIB细胞毒性作用以及采用台盼蓝染色法检测了TCs对刺激转化的人外周血单个核细胞（PeriphejralBloodMononuclearCen，PBMC）的细胞毒性作用；以合胞体形成抑制实验检测了TCS对实验株HIV-1ms诱导C8166细胞致细胞病变的抑制作用；以捕捉HIV-1p24抗原ELISA方法检测TCS对实验．株HIV-1IIIB在急性感染C8166，细胞和慢性感染Hg细胞中复制的抑制作用、临床分离株HIV-1KMO18在PBMC中复制的抑制作用、耐药株HIV-174v在C8166细胞中复制的抑制作用。其次，利用荧光实时定量RT-PCR检测了TCS对HIV-IIIB吸附和融合宿主细胞的抑制作用；采用高效液相色谱（HighPerformanceLiquidChromatograPhy，HPLC）检测了TCS脱HIV-IRNA腺嘿呤作用；另外还检测了TCS对病毒颗粒的直接杀伤作用、TCS对HIV感染和未感染细胞融合的抑制以及对HIV重组逆转录酶活性的抑制作用。最后，利用以蛋白工程技术构建的14个TCD突变体研究其抗HIV的构效关系，其中活性中心突变体：结果表明，TCS不仅能够有效抑制实验株HIV-1mB在C8166细胞中的复制和HIV-1ms诱导宿主细胞的病变作用，还能抑制临床分离株HIV-1KM018在PMBC中的复制和耐药株HIV-174v在C8166细胞中的复制，但TCS对HIV-1在慢性感染H9细胞中的复制无直接抑制作用。TCS不能抑制HIV-1进入宿主细胞；对感染细胞和未感染细胞的融合没有抑制作用；TCS也不能抑制HIV-1重组逆转录酶活性；TCS对病毒颗粒的直接杀伤作用不大；但TCS能够使裸露的HIV-1RNA脱腺漂呤，可能TCS的脱缥岭活性或其它酶活性直接损伤病毒或者病毒感染细胞的核酸，而胞质腺嗦岭含量的增高则可以导致线粒体膜电位的降低、细胞色素C的释放、活性氧的增加和抗凋亡因子表达的下降，结果使感染细胞更多的凋亡，这可能是TCS抗HIV的一个机制。结果也表明，活性中心突变体TCSM（120-123）与TCSE160A/E189A，在失去绝大部分R工活"性的同时，也几乎完全失去抗HIV活性。、而另一个活性中心突变体TCSR122G，RI活性下降1的倍，却仍保留一定的抗HIV活性。TcSC末端删除突变体（TCSC2，TCSC4和TCSC14）抗HIV活性的下降（1.4-4.8倍）与其R1活性呈平行下降（1.2-3.3倍）。这些结果表明TCS抗HIV-1活性与其R1活性显著相关，但似乎又不是唯一的决定因素，因为我们发现二个分别在C末端加上末端19个氨基酸延伸肤或KDEL信号肤的突变体TCS饥触与TCSKDEL，虽然保留全部的RI活性，但却几乎完全失去抗HIV活性，表明有其它机制介入了TCS的抗HIV-1活性。TCS抗原决定簇位点突变后对TCS抗HIV-1活性没有显著影响，但当在抗原决定簇突变体所引入的Cys残基上加上PEG漱后，这些突变体则显著降低了抗HIV-1的活性。

Deep centers in AlGaAs/GaAs GRIN-SCH SQW laser structures grown by MBE and MOCVD

The deep centers in AlGaAs/GaAs graded index-separate confinement heterostructure single quantum well (GRIN-SCHSQW) laser structures grown by MBE and MOCVD have been investigated using deep level transient spectroscopy (DLTS) technique, The majority and minority carrier DLTS spectra show that the deep (hole and electron) traps (Hi and E3), having large capture cross sections and concentrations, are observed in the graded n-AlxGa1-xAs layer of laser structures in addition to the well-known DX centers. For laser structures grown by MBE, the deep hole trap H1 and the deep electron trap E3 may be spatially localized in the interface regions of discontinuous variation Al mole fraction of the n-AlxGa1-xAs layer with x = 0.20-0.43. For laser structures grown by MOCVD, the deep electron trap E3 may be spatially localized in the n-AlxGa1-xAs layer with x = 0.18-0.30, and the DX center may be spatially localized in the interface regions of discontinuous variation Al mole fraction of the AlxGa1-xAs layer with x = 0.22-0.30.

Numerical analysis of four-wave-mixing based multichannel wavelength conversion techniques in fibers

We numerically investigate four-wave-mixing (FWM) based multichannel wavelength conversion for amplitude-modulated signals, phase-modulated signals, together with mixed amplitude and phase modulated signals. This paper also discusses the influence of stimulated Brillouin scattering (SBS) effects on high-efficiency FWM-based wavelength conversion applications. Our simulation results show that DPSK signals are more suitable for FWM-based multichannel wavelength conversion because the OOK signals will suffer from the inevitable datapattern-dependent pump depletion. In future applications, when the modulation format is partially upgraded from OOK to DPSK, the influence of OOK signals on the updated DPSK signals must be considered when using multichannel wavelength conversion. This influence becomes severe with the increase of OOK channel number. It can be concluded that DPSK signals are more appropriate for both transmission and multichannel wavelength conversion,especially in long haul and high bit-rate system.

Coupled AlxGa1-xAs-AlAs distributed Bragg reflectors for high brightness AlGaInP light emitting diodes

A novel coupled distributed Bragg reflector (DBR) with double thickness periods was theoretically analyzed based on the spontaneous radiation properties of high brightness AlGaInP light emitting diodes(LED). Several important factors were considered including spontaneous radiation angle distribution, absorption and FTR of DBR. Calculation results showed that the optimum optical thickness of single layer of the DBR deviates from 1/4 lambda. AIGaInP high brightness light emitting diodes both with Al0.5Ga0.5As/AlAs coupled DBR and with conventional DBR were fabricated by metalorganic chemical vapor deposition(MOCVD). X-ray double crystal diffraction and reflection spectrum were employed to determine the thickness and reflectivity of the DBR. It was found that reflectivity of coupled DBR is less sensitive to incident angle than conventional DBR, higher external quantum efficiency of light emitting diodes with coupled DBR was obtained than that with conventional DBR.