Hg_(1-x)Cd_xTe混晶中光学声子与电子的相互作用

本文用双格点模型描写Hg_(1-x)Cd_xTe 混晶的双模式光学振动,计算了T=77K时长波TO和LO声子的频率,理论值与实验值符合较好.引入双模式的Callen有效电荷,导出了Hg_(1-x)CdxTe 混晶中光学声子与电子相互作用的矩阵元.对于n型Hg_(?)Cd_(0.2)Te,计算了光学声子散射对自由载流子吸收系数的贡献(T=90K,λ=20μm),并与声学声子散射、电离杂质散射和无序散射进行了比较,结果表明光学声子散射是主要散射机构.     

薄膜电致发光器件中硫空位的散射作用

利用分波法计算了薄膜电致发光器件中硫空位对电子的散射速率,并将其与其它散射机制进行了比较。研究了散射速率与电子能量及温度的关系,并比较了硫空位俘获电子前后的散射速率。提出硫空位的存在是阻碍获得高亮度蓝色薄膜电致发光器件的关键。     

非均匀电离层中VLF辐射源在海面上产生的场

为了研究甚低频(very low frequency, VLF)电磁波对电离层中目标的近场散射机制,提出了一种VLF电磁波在该环境中对有限长金属和介质柱体近场散射的计算方法。首先,通过定义散射系数和交叉散射系数,分析各向异性电离层中电型波和磁型波激励下的散射矩阵;然后,根据积分方程法和矩量法,计算得到各向异性电离层中有限长金属和介质柱体的近区散射场和表面电流半解析表达式;最后,通过各向异性电离层中VLF波的特征波分析,给出柱体近区散射场中寻常波(O波)和非寻常波(E波)分量空间分布情况。计算结果表明：电离层中VLF波在金属和介质目标表面激励了不同的电流,并在不同的电离层环境参数、柱体尺寸和入射角度下产生相应的近场散射和耦合散射;通过对比O波和E波表面电流分布和散射分量,进一步揭示了VLF波与暴露在均匀等离子体环境中的柱体目标的散射机理。本文的计算方法和结果可为电离层中散射通信和目标探测提供理论依据。

     

三维机翼前缘影区爬行波RCS研究

分析了三维机翼前缘影区的爬行波散射机理,建立了前缘影区爬行波的雷达散射截面(RCS)计算模型.根据光滑凸曲面的一致性绕射理论(UTD)给出爬行波的后向散射远区电磁场计算公式,按RCS定义计算爬行波散射贡献.采用微分几何原理分析任意凸曲面上的爬行波短程线特性,根据爬行波在光滑凸曲面上的短程线测地曲率为零的条件,给出一种三维机翼表面短程线计算方法.对三维机翼前缘爬行波进行计算和测试,并计算分析不同机翼参数对前缘影区爬行波的影响.计算结果和测试结果吻合良好,表明该方法计算爬行波RCS快捷有效,可应用于工程分析.     

电波传播

0319926雨介质中简单目标的相干散射场[刊]/李应乐//电波科学学报.—2003,18(2).—200～202,215(L)利用叠加原理,导出了离散雨介质中相干散射场与目标散射场的具体表达式,数值计算了雨介质中相干散射场与降雨率的关系,计算结果表明:波的衰减不     

电子耗空对喷焰尘埃等离子体离子波不稳定性的影响

在离子波不稳定性增长率的计算过程中增加对自洽尘埃电荷数的考虑, 以考察电子耗空效应对尘埃等离子体离子波不稳定性增长率的影响.通过比对多个算例的计算结果发现:随着尘埃数密度的增大, 电子耗空的加剧可以导致不稳定性增长率减小; 喷焰释放早期的离子波不稳定性增长率可以更低; 无论是尘埃数密度还是中性分子数密度单独增大, 均可以导致离子波不稳定性增长率的减小.这表明现有理论方法中隐含的假设不是恒成立.     

中断波多普勒谱的线型分析

本文通过对海面波动引起的微波后向散射谱的谱密度分析发现多普勒谱可以分解成不同的分量，即以高斯线型为代表的Ｂｒａｇｇ后向散射和以Ｌｏｒｅｎｔｚｉａｎ或Ｖｏｉｇｔｉａｎ线型为代表的快速Ｂｒａｇｇ散射。据推测，快速Ｂｒａｇｇ散射是由中断波散射引起的，其散射机理在自然界中是非Ｂｒａｇｇ。为检验散射过程中有代表意义的符合上述谱线分析这个假设，我们在一个波池内做了性能试验。对中断波的多普勒的线型进行了分析。发     

随机粗糙面上目标散射差值计算的快速互耦迭代方法

用粗糙面上方有目标和无目标时空间散射场的差值计算的雷达散射截面,称为差场雷达散射截面.本文推导TE波入射下电场积分方程(EFIE),直接求解散射差场.本文提出目标与粗糙面之间的互耦迭代的计算方法,散射场纳入了目标与粗糙面之间复杂的相互作用,给出了迭代过程中纳入的粗糙面长度的选择.用Monte-Carlo方法,计算了P-M谱粗糙海面上方二维圆柱和方柱的散射,说明目标的几何结构对散射方向图的影响.     

合成孔径雷达散射波干扰研究

本文针对合成孔径雷达(SAR)的特性,提出一种全新的有源干扰方式:散射波干扰.分析了散射波干扰信号的特点和散射波干扰对SAR图像的干扰效果,从原理上说明了散射波干扰相对于直达波干扰的优势.分别针对星载SAR和机载SAR进行了散射波干扰仿真实验,给出了仿真结果.     

自由电子激光器的进展

一、进展概况高功率短波长和波长连续可调高功率激光器一直是激光研究的两个主要方向,自由电子受激辐射正是为实现这种目的的一种新途径.原理上,利用自由电子受激辐射可以实现从微波至X射线、γ射线宽波长连续可调的高功率、高效率微波与光激射器.因此,它已引起人们的普通重视.早在1933年,有人根据量子理论提出利用"摆动"或"波动"电子束与电磁波相互作用产生"受激散射"的概念.两个散射区域分别为:(1)康普顿散射:两波互作用(或单个电子互作用);(2)拉曼散射:三波互作用(或集团电子互作用).1951年莫茨(Motz)提出自由电子受激辐射理论.他认为,当电子行经电场或磁场时产生辐射,辐射的频率取决于电子的速率,电子能量从1兆电子伏到1千兆电子伏范围内可产生从微波至硬X射线频谱.他认为,将电子束聚焦,可以使一群电子相干地辐射,相干辐射功率比非相干辐射约高     

Resolution Enhancement Technology:Integrated Process Solutions using OPC

DUV lithography, using the 248 nm wavelength, is a viable manufacturing option for devices with features at 130 nm and less. Given the low kl value of the lithography, integrated process development is a necessary method for achieving acceptable process latitude. The application of assist features for rule based OPC requires the simultaneous optimization of the mask, illumination optics and the resist.Described in this paper are the details involved in optimizing each of these aspects for line and space imaging.A reference pitch is first chosen to determine how the optics will be set. The ideal sigma setting is determined by a simple geometrically derived expression. The inner and outer machine settings are determined, in turn,with the simulation of a figure of merit. The maximum value of the response surface of this FOM occurs at the optimal sigma settings. Experimental confirmation of this is shown in the paper.Assist features are used to modify the aerial image of the more isolated images on the mask. The effect that the diffraction of the scattering bars (SBs) has on the image intensity distribution is explained. Rules for determining the size and placement of SBs are also given.Resist is optimized for use with off-axis illumination and assist features. A general explanation of the material' s effect is discussed along with the affect on the through-pitch bias. The paper culminates with the showing of the lithographic results from the fully optimized system.     

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.     

Theoretical analysis of the relationship between the Brillouin gain coefficient and the strain in the optical-fiber sensors

The relation between the power of the Brillouin signal and the strain is one of the bases of the distributed fiber sensors of temperature and strain. The coefficient of the Bfillouin gain can be changed by the temperature and the strain that will affect the power of the Brillouin scattering. The relation between the change of the Brillouin gain coefficient and the strain is thought to be linear by many researchers. However, it is not always linear based on the theoretical analysis and numerical simulation. Therefore, errors will be caused if the relation between the change of the Brillouin gain coefficient and the strain is regarded as to be linear approximately for measuring the temperature and the strain. For this reason, the influence of the parameters on the Brillouin gain coefficient is proposed through theoretical analysis and numerical simulation.     

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.     

Novel fiber-optical interferometer with miniaturized probe for in-hole measurements

Today, micro-system technology and the development of new MEMS （Micro-Electro-Mechanical Systems） are emerging rapidly. In order for this development to become a success in the long run, measurement systems have to ensure product quality. Most often, MEMS have to be tested by means of functionality or destructive tests. One reason for this is that there are no suitable systems or sensing probes available which can be used for the measurement of quasi inaccessible features like small holes or cavities. We present a measurement system that could be used for these kinds of measurements. The system combines a fiber optical, miniaturized sensing probe with low-coherence interferometry, so that absolute distance measurements with nanometer accuracy are possible.     

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.     

Study of waveguide coupling efficiency in hybrid silicon lasers

This paper presents a new method to increase the waveguide coupling efficiency in hybrid silicon lasers. We find that the propagation constant of the InGaAsP emitting layer can be equal to that of the Si resonant layer through improving the design size of the InP waveguide. The coupling power achieves 42% of the total power in the hybrid lasers when the thickness of the bonding layer is 100 nm. Our result is very close to 50% of the total power reported by Intel when the thickness of the thin bonding layer is less than 5 nm. Therefore, our invariable coupling power technique is simpler than Intel＇s.     

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.     

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.