雾天环境下激光传输的衰减特性研究

激光在大气中传输时容易受天气的影响,因为雨、雪、雾等恶劣天气对激光有严重的衰减作用,会使通信的稳定性变差.因此分析激光在不同天气条件下的传输效应和衰减特性非常有必要.本文根据辐射雾和平流雾中含水量和能见度的经验关系,分析了雾天气对激光大气传输衰减的计算公式,并对三种常用的雾衰减经验模型进行了Matlab数值仿真,得出了激光衰减系数和雾天气能见度的关系.     

激光大气传输的雨雾衰减特性研究

各种特殊天气的影响是制约无线光通信发展的重要因素,雨雾等天气对激光信号传输的衰减影响很大。主要研究了各种雨雾天气对激光大气传输的衰减特性,根据Mie散射理论分析了精确计算激光信号衰减的方法,并对几种常用的雨雾衰减经验模型进行Matlab数值仿真,通过分析从中得出激光衰减系数和雨雾天气能见度的关系。     

雾衰减经验模型的适用性分析

雾衰减经验模型的计算是预测雾衰减的一种重要方法。为了将雾衰减经验模型应用到实际中进行适用性分析, 从米氏散射理论出发, 采用理论推导和仿真分析的方法, 计算了Kruse模型、Kim模型和Ijaz模型中激光在不同能见度下的衰减, 分析了3个模型在计算衰减系数时的差异, 并通过搭建自由空间光通信实验平台, 将实验结果与仿真结果对比分析。结果表明, 650nm波长的激光在雾衰减信道下的衰减结果与Kim衰减模型更接近。此研究结论为西安地区自由空间光通信系统雾衰减系数分析提供了参考依据。     

雾对10.6μm红外辐射的衰减特性研究

基于gamma雾滴尺寸分布模型及辐射雾和平流雾含水量与能见度的经验关系,计算并回归得到了平流雾和辐射雾对10.6μm红外辐射的衰减与含水量和能见度的关系,其对浓辐射雾得到的雾衰减与含水量的线性关系与文献所给实验结果和半经验公式均有很好的一致性.最后对雾的红外衰减和可见光衰减进行了比较,结果表明浓平流雾对10.6μm红外辐射的雾衰减大于可见光的雾衰减.     

雾对毫米波传输衰减特性研究

本文在计算水介电常数的基础上,在瑞利近似的条件下,针对平流雾和辐射雾并结合能见度和含水量的关系,从频率、能见度、温度三方面对毫米波传输衰减进行了数值计算和仿真,最后给出了雾衰减的相关结论,对极高频电磁波在雾天气情况下的传输衰减研究有一定的参考价值。     

雾对10.6μm红外辐射的衰减特性研究

基于gamma雾滴尺寸分布模型及辐射雾和平流雾含水量与能见度的经验关系，计算并回归得到了平流雾和辐射雾对10.6μm红外辐射的衰减与含水量和能见度的关系，其对浓辐射雾得到的雾衰减与含水量的线性关系与文献所给实验结果和半径经验公式均很好的一致性，最后对雾的红外衰减和可见光衰减进行了比较，结果表明浓平流雾对10.6μm红外辐射雾衰减大于可见光的雾衰减。     

降雨和雾气天气下自由空间光通信性能研究

天气的影响会导致自由空间光通信系统性能恶化。利用Mie理论和两种雨滴谱分布模型,计算了不同降雨量下大气激光传输的衰减;根据Kim和AlNaboulsi模型计算了激光在不同能见度下的衰减。研究了降雨和雾气对自由空间光通信系统性能的影响,分析了不同降雨量时降雨和雾气天气条件下传输距离与误码率的关系以及发射功率与误码率的关系。结果表明,降雨量不同会影响通信距离;雾天衰减比雨天衰减更为严重,通信距离变短,为保证系统正常工作,可以适当加大发射功率。     

激光致盲武器雨雾条件下传输机理研究

非致命激光致盲武器在恶劣天气尤其是雨雾天气下使用时,打击效果较差,不能达到预期的致盲效果。因此,必须研究一种激光自动调节系统,而设计这个系统最关键的问题就是研究激光在雨雾条件下的传输机理,所以本文基于Mie散射理论分别研究了激光在雨中、雾中以及雨雾共存三种条件下的衰减情况,得到激光透过率与降雨量、雾浓度以及传输距离之间的关系。对其进行Matlab仿真,结果表明激光透过率随着降雨量的增大、雾浓度以及传输距离的增加而减小,且衰减明显。     

雾天多次散射对激光透射仪能见度测量的影响

为了分析雾天多次散射引起的激光透射仪能见度测量误差，结合激光大气透射仪的系统参量，基于平流雾和辐射雾分布模型，采用蒙特卡洛法对激光在雾中的传输特性进行了理论分析和数值模拟，获得了雾天透过率数据，并计算得到了多次散射引起的能见度误差。结果表明，在雾天气下随着空气中含水量的增多，多次散射越明显，透过率测量误差越大，辐射雾的透过率相对误差高达116.76%；同等条件下，当接收机直径为100cm时，辐射雾多次散射引起的能见度测量误差为19.30%；同时选取较小的接收机直径可以减小多次散射引起的能见度测量误差。因此, 在雾天应用激光透射仪进行能见度测量时，需考虑多次散射的影响。此研究结果对实际雾天气下激光大气透射仪能见度的测量具有重要的指导意义。     

激光在大气中传输衰减特性研究

激光在大气中传输特性的研究是激光探测与制导、激光通信等光电系统设计中的一个主要问题.利用衰减的经验模型和Mie理论,分别计算了不同大气能见度下的霾粒子对激光大气传输产生的衰减,并对这两种方法计算的结果进行比较分析;再根据Mie理论和云雾的尺度分布模型计算了云雾的激光衰减.结果表明,在近红外波段对于对流层大气中霾粒子的衰减预测应用Mie理论计算更合理;云雾引起的衰减一般较大,并且随着能见度的减小,衰减增加较快.因此,当Vb＜15km时,霾引起的衰减需要考虑;当Vb较小时,云雾的激光衰减是限制系统性能的主要因素.     

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.