二维光子晶体波导和微腔缺陷态研究

利用二维三角晶格及正方晶格介质柱光子晶体TE偏振的禁带与介质柱半径的变化关系,分析了二维光子晶体缺陷态的分布.根据光子晶体波导间的耦合作用,计算其耦合长度设计合理的定向耦合器.通过分析波导与微腔的耦合特性,选取不同的传输方向,可以设计多种基于光子晶体波导与微腔耦合的波分复用系统.     

基于锯齿口和多支路的二维光子晶体出射光集束

光子晶体波导具有传输速率大、损耗率低、稳定性好等特点,在光集成、光信息传输等领域具有十分广阔的应用前景.然而作为亚波长波导,由于存在衍射极限,光子晶体波导的出射光会发散到各个方向,影响出射光集束.为解决光子晶体波导出射端光场控制问题,提出了一种新型的二维正方晶格光子晶体出射光集束的结构.该结构通过在波导出射端表面引入锯齿口结构和多支路通道,大幅度提升了出射光的辐射距离.利用时域有限差分法分析结果表明,具有3个锯齿口和2条支路的正方晶格光子晶体能够实现最佳的出射光集束,辐射距离高达200 μm,该辐射距离约为单波导出射端结构的25倍,且该结构在200 μm处的辐射效率可达53％.     

基于多模干涉的二维三角晶格光子晶体分束器

光分束器光接入系统的核心器件,是光子多功能设 备和系统的关键构成模块,为满足急速增长的数据通信业务对光分束器的需求,本文在完整 三角晶格光子晶体中引入五条平行光子晶体波导组成多模干涉 系统,利用自成像效应的多模波导与微腔耦合,提出了一种新型二维三角晶格光子晶体四端 口分束器。利 用时域有限差分法进行仿真分析,结果表明:在一定范围内通过改变输出端四个耦合微腔内 的介质柱半径, 可以保证在分束器拥有较高的透射率的同时,且能实现输出能量的均分或在一定范围内的自 由分配。     

光子晶体波导定向耦合功分器的设计

将相互耦合的3平行光子晶体单模波导看成一个多模干涉系统,通过研究二维正方晶格光子晶体波导多模干涉的自映像效应,优化设计了一种新型1×2光子晶体波导定向耦合分束器,采用时域有限差分法对其传输特性进行模拟分析。设计过程中,根据多模干涉耦合区中周期出现的双重像的位置确定两个单模输出波导的位置,通过改变输出波导和耦合区连结的一个介质柱位置构成波导微腔结构,改变耦合区中的模场分布,实现模式匹配,从而明显减小分束器的反射损耗。计算结果表明,移动介质柱距离输出单模波导和多模波导连结处1.85a位置处时,对于波长为1.55μm的入射光,该分束器的透射率可高达99.04%。     

二维三角形光子晶体带隙与耦合特性研究

利用二维三角晶格介质柱光子晶体TE偏振的禁带与介质柱半径的变化关系,分析了二维光子晶体的带隙分布及斜边耦合特性.结果表明,光子禁带的大小受到构成光子晶体的介电材料的空间排列分布以及介质柱半径大小的影响;束缚在光子晶体中的光波可以在波导和谐振腔中进行传输,达到选择输出光波的目的.     

二维光子晶体波导的能带分析

设计了在25×13的二维圆柱正方晶格中心引入线缺陷构成的光子晶体波导,利用平面波展开法(PW E)方法计算并仿真了该波导的能带分布,分析出其带隙分布与介质柱折射率和占空比的关系,总结出了能带与两者之间的变化规律,得出了存在最大带隙结构的波导参数是介质柱的折射率为6.9,占空比2r/a=3.6,对于实际制作光子晶体波导提供了理论指导。     

空气孔型光子晶体带隙及波导耦合特性研究

为了研究2维三角晶格空气孔型光子晶体TE模和TM模偏振的禁带宽度与介质柱半径的变化关系,采用平面波展开法数值计算和分析了空气孔型光子晶体的带隙分布及波导耦合特性。结果表明,光子禁带的宽度会随着介质柱半径的大小而变化,束缚在光子晶体中的光波可以在波导和谐振腔中高效率地传输,达到选择输出光波的目的。这种特性在光学集成电路中具有重要而潜在的应用价值。     

折射率可调的二维光子晶体设计与特性

光子晶体在传感、滤波和光子晶体激光器等方面具有很重要的应用价值。设计了一种基于改变缺陷介质折射率的可调谐二维正方晶格和三角晶格光子晶体激光器微腔,在平面光子晶体薄板中引入点缺陷磷酸氧钛钾(KTP),在KTP两端施加交流电场控制KTP晶体折射率变化。实验中随着KTP晶体折射率逐渐增大,正方晶格光子晶体禁带数量减少,归一化频率减小,禁带宽度基本不变;而三角晶格光子晶体禁带逐渐变窄,且向低频方向移动。最后,用平面波展开法分析了晶体的能带结构,得到理论上的描述,验证了实验结果。     

二维光子晶体窄带滤波器研究

由于光子晶体存在带隙,只要在完整的二维光子晶体中引入线缺陷,那么原来处于禁带处特定波长的光也能沿着形成的波导传播,从而该光子晶体就具备了滤波的功能,再在线型波导的一侧设计个点缺陷,利用时域有限差分法分析发现,在缺陷处耦合出来的光不仅仅光强增大了,而且半高宽也变小了,这就与窄带滤波器的功能十分吻合。此外,只要根据光子晶体的晶格常数和椭圆介质柱的半径与窄带滤波器的中心波长关系,通过调整光子晶体的晶格常数和介质柱的半径,就可以改变窄带滤波器的中心波长。     

GeSbSe光子晶体波导结构设计及传输特性研究

利用平面波展开法计算Ge Sb Se基质光子晶体带隙,研究光子晶体波导中带隙与空气孔(或介质柱)半径的变化关系,并结合光子晶体波导的工作波长,设计出周期为500 nm,半径为150 nm的三角晶格空气孔型Ge Sb Se光子晶体波导。采用时域有限差分法模拟所设计的直线型光子晶体波导和60°弯曲光子晶体波导的传输特性,模拟结果显示在传统结构光子晶体波导中,直线型光子晶体波导具有很高的光学传输效率,但在60°弯曲型波导中的传输效率较低,分析原因为光子晶体波导直线区域与弯曲区域光的传播模式不同。因此对60°弯曲型Ge Sb Se光子晶体波导进行了结构优化,优化后的光子晶体波导可以在较宽的波长范围内具有很高的传输效率。     

Development of the readout system for waveguide multilayer optical card

Waveguide multilayer optical card （WMOC） is a novel storage device of three-dimensional optical information. An advanced readout system fitting for the WMOC is introduced in this paper. The hardware mainly consists of the light source for reading, WMOC, motorized stages addressing unit, microscope imaging unit, CCD detecting unit and PC controlling ＆ processing unit. The movement of the precision motorized stage is controlled by the computer through Visual Basic （VB） language in software. A control panel is also designed to get the layer address and the page address through which the position of the motorized stages can be changed. The WMOC readout system is easy to manage and the readout result is directly displayed on computer monitor.     

Nanoimprint Lithography -A Next Generation High Volume Lithography Technique

IntroductionNanoimprint Lithography is a well-acknowl-edged low cost, high resolution, large area pattern-ing process. It includes the most promising methods,high-pressure hot embossing lithography (HEL) [2],UV-cured imprinting (UV-NIL) [3] and micro contactprinting (m-CP, MCP) [4]. Curing of the imprintedstructures is either done by subsequent UV-lightexposure in the case of UV-NIL or by cooling downbelow the glass transition temperature of the ther-moplastic material in case of HEL…     

Collinear phase-matching study of terahertz-wave generation via difference frequency mixed in GaAs and Inp

The collinearly phase-matching condition of terahertz-wave generation via difference frequency mixed in GaAs and InP is theoretically studied. In collinear phase-matching, the optimum phase-matching wave hands of these two crystals are calculated. The optimum phase-matching wave bands in GaAs and lnP are 0.95-1.38μm and 0.7-0.96μm respectively. The influence of the wavelength choice of the pump wave on the coherent length in THz-wave tuning is also discussed. The influence of the temperature alteration on the phase-matching and the temperature tuning properties in GaAs crystal are calculated and analyzed. It can serve for the following experiments as a theoretical evidence and a reference as well.     

Effects of the alloy compositions on the phonon-polaritons in ternary mixed crystals

Composition dependence of bulk and surface phonon-polaritons in ternary mixed crystals are studied in the framework of the modified random-element-isodisplacement model and the Bom-Huang approximation. The numerical results for Several Ⅱ - Ⅵ and Ⅲ- Ⅴ compound systems are performed, and the polariton frequencies as functions of the compositions for ternary mixed crystals AlxGa1-xAs, GaPxAS1-x, ZnSxSe1-x, GaAsxSb1-x, GaxIn1-xP, and ZnxCd1-xS as examples are given and discussed. The results show that the dependence of the energies of two branches of bulk phonon-polaritons which have phonon-like characteristics, and surface phonon-polaritons on the compositions of ternary mixed crystals are nonlinear and different from those of the corresponding binary systems.     

Influence of PVK ： NPB hole transporting layer on the characteristics of organic light-emitting devices

A doping system consisting of NPB and PVK is employed as a composite hole transporting layer （CHTL）. By adjusting the component ratio of the doping system, a series of devices with different concentration proportion of PVK ： NPB are constracted. The result shows that doping concentration of NPB enhances the competence of hole transporting ability, and modifies the recombination region of charge as well as affects the surface morphology of doped film. Optimum device with a maximum brightness of 7852 cd/m^2 and a power efficiency of 1.75 lm/W has been obtained by choosing a concentration proportion of PVK ： NPB at 1：3.     

New insert layer structure OLEDs

An insert layer structure organic electroluminescent device（OLED） based on a new luminescent material （Zn（salen）） is fabricated. The configuration of the device is ITO/CuPc/NPD/Zn（salen）/Liq/LiF/A1/CuPc/NPD/Zn（salen）/Liq/LiF/A1. Effective insert electrode layers comprising LiF（1nm）/Al（5 nm） are used as a single semitransparent mirror, and bilayer cathode LiF（1 nm）/A1（100 nm） is used as a reflecting mirror. The two mirrors form a Fabry-Perot microcavity and two emissive units. The maximum brightness and luminous efficiency reach 674 cd/m^2 and 2.652 cd/A, respectively, which are 2.1 and 3.7 times higher than the conventional device, respectively. The superior brightness and luminous efficiency over conventional single-unit devices are attributed to microcavity effect.     

Analysis of error performance on Turbo coded FDPIM

Due to variable symbol length of digital pulse interval modulation（DPIM）, it is difficult to analyze the error performances of Turbo coded DPIM. To solve this problem, a fixed-length digital pulse interval modulation（FDPIM） method is provided. The FDPIM modulation structure is introduced. The packet error rates of uncoded FDPIM are analyzed and compared with that of DPIM. Bit error rates of Turbo coded FDPIM are simulated based on three kinds of analytical models under weak turbulence channel. The results show that packet error rate of uncoded FDPIM is inferior to that of uncoded DPIM. However, FDPIM is easy to be implemented and easy to be combined, with Turbo code for soft-decision because of its fixed length. Besides, the introduction of Turbo code in this modulation can decrease the average power about 10 dBm, which means that it can improve the error performance of the system effectively.     

A method for calculating the center position of collimated light

It is a key problem to accurately calculate beam spots＇ center of measuring the warp by using a collimated laser. A new method, named double geometrical center method （DGCM）, is put forward for the first time. In this method, a plane wave perpendicularly irradiates an aperture stop, and a charge couple device （CCD） is employed to receive the diffraction-beam spots, then the geometrical centers of the fast and the second diffraction-beam spots are calculated respectively, and their mean value is regarded as the center of datum beam. In face of such adverse instances as laser intension distributing defectively, part of the image being saturated, this method can still work well. What＇s more, this method can detect whether an unacceptable error exits in the courses of image receiving, processing and calculating. The experimental results indicate the precision of this method is high.     

Cost-effective test solutions for smart card and other integrated flash applications

From its emergence in the late 1980s as a lower cost alternative to early EEPROM technologies, flash memory has evolved to higher densities and speedsand rapidly growing acceptance in mobile applications.In the process, flash memory devices have placed increased test requirements on manufacturers. Today, as flash device test grows in importance in China, manufacturers face growing pressure for reduced cost-oftest, increased throughput and greater return on investment for test equipment. At the same time, the move to integrated flash packages for contactless smart card applications adds a significant further challenge to manufacturers seeking rapid, low-cost test.     

An improved parallel thinning algorithm with two subiterations

The parallel thinning algorithm with two subiterations is improved in this paper. By analyzing the notions of connected components and passes, a conclusion is drawn that the number of passes and the number of eight-connected components are equal. Then the expression of the number of eight-connected components is obtained which replaces the old one in the algorithm. And a reserving condition is proposed by experiments, which alleviates the excess deletion where a diagonal line and a beeline intersect. The experimental results demonstrate that the thinned curve is almost located in the middle of the original curve connectivelv with single pixel width and the processing speed is high.