光子晶体中原子的受激辐射(英文)

受激辐射机制的研究是光子晶体激光器设计中的一个基本问题。采用全量子理论 分析光子晶体中单个二能级原子的受激辐射。讨论的原子能级间跃迁频率在光子带隙内且接 近带隙边缘。在光子晶体中初态光场影响着系统的行为,激发态粒子数布居出现了有趣的现 象：反束缚、周期振荡和准周期振荡。受激辐射的性质明显与初始态的光场和原子激发态能级 相对光子带隙的位置有关。     

光子晶体中原子的受激辐射(英文)

受激辐射机制的研究是光子晶体激光器设计中的一个基本问题.采用全量子理论分析光子晶体中单个二能级原子的受激辐射.讨论的原子能级间跃迁频率在光子带隙内且接近带隙边缘.在光子晶体中初态光场影响着系统的行为,激发态粒子数布居出现了有趣的现象:反束缚、周期振荡和准周期振荡.受激辐射的性质明显与初始态的光场和原子激发态能级相对光子带隙的位置有关.     

玻色-爱因斯坦凝聚(BEC)中的辐射修正

在最近几年随着对玻色-爱因斯坦凝聚（BEC）研究的迅速发展，关于BEC各种性质，尤其是其光学性质的研究引起了人们的关注。现已有大量的报道．本文将讨论BEC中的自发辐射和兰姆位移修正。我们知道，原子被激发后，会自发辐射跃迁到较低的能级，同时发射出光子。如果在共振频率的光模场中已有N个光子存在，由于光场和原子的相互作用，原子则会受激辐射，受激辐射速率为自发辐射速率的N倍。在基态存在N个简并的原子时是否可以产生原子辐射的类似受激过程呢？结论是肯定的。总的辐射速率为自发辐射速率与受激过程速率的和，即，其中，ν为…     

多光子J-C模型的研究

本文推广二能级原子J-C模型到多光子过程。求得在存在偏调情况下,单模相干场对二能级原子激发时的光子数几率分布函数,由此研究了原子受激辐射性质。     

由Na_2-Na双光子混合共振和四波混频产生的可调谐紫外相干辐射

由与Na_2-Na双光子混合共振相关联的四波混频过程产生可调谐紫外相干辐射。当以614.5～617.4nm的染料激光泵浦钠蒸气时,第一个光子将钠分子从基态X_1∑_g~+激发到A~1∑_u~+态;通过Na_2~*-Na近共振碰撞能量转移过程,将处于基态3S的钾原子激发到3P(3/2),(3/2)态;第二个光子将钠原子共振激发到5S态,从而产生5S→4P的受激辐射和4P→4S的串级受激辐射。而在离共振激发时,除上述受激辐射(或串级受激辐射)外,还存在分别起始于3P_(1/2)和3P(3/2)态的受激喇曼散射。上述受激辐射(或串级受激辐射)和受激喇曼散射分别与泵浦光的     

钠蒸气中基于Na-Na碰撞能量转移的光泵级联辐射

本文报道了钠蒸气中基于Na-Na近共振碰撞能量转移而产生的光泵受激辐射。当双光子共振激发4d能级时,可探测到起始于4f能级的受激辐射;而当进行4f能级的偶极禁戒双光子共振激发时,则可产生起始于4f能级的受激辐射及其跟随的级联受激辐射。文中对有关过程进行了讨论。     

级联型三能级原子受激辐射的相干性质

本文以级联型三能级原子为对象,利用一阶关联函数的因式分解式可以定义场为光学相干的,运用数值求和的方法,将电场关联函数及电场负频正频的积作图比较,分别讨论了原子初始处于不同能级时的受激辐射的相干性质,并讨论了二模场与原子耦合系数不等这种更一般情况。 并指出,在本文所及的较小平均光子数的情况下,各种因素对受激辐射相干性质的影响皆可通过对初振荡半周期内形态的影响而体现出来。     

基于半导体光放大器临界激射状态的同相波长转换

基于半导体光放大器处于放大和激射之间的临界状态 ,实现了同相波长转换 ,转换后光信号与泵浦光信号有相同的比特系列 .运用放大器中存在的自发辐射光子诱发的受激辐射和入射信号光子诱发的受激辐射之间的竞争很好地解释了实验结果 .结果表明 ,此种波长转换结构简单、输出消光比不退化     

基于半导体光放大器临界激射状态的同相波长转换

基于半导体光放大器处于放大和激射之间的临界状态,实现了同相波长转换,转换后光信号与泵浦光信号有相同的比特系列.运用放大器中存在的自发辐射光子诱发的受激辐射和入射信号光子诱发的受激辐射之间的竞争很好地解释了实验结果.结果表明,此种波长转换结构简单、输出消光比不退化.     

受激辐射的性质和竞争效应

本文分三部分,第一部分为受激辐射的理论描述。用爱因斯坦理论和经典、半经典、量子理论简要地描述受激辐射的性质.第二部分为受激辐射的竞争效应。在激光建立过程中,受激辐射几率是一个变量,不同模式(或不同状态)的光之间存在激烈的竞     

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.     

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.     

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.     

Towards Mobile Ubiquitous Service Environment

In this article we present a perspective on future vision of mobile communications and services which is referred to as Mobile Ubiquitous Service Environment (MUSE). Based on analysis of wireless communications and services, we exploit a conceptual model for MUSE via a top-down approach. The conceptual model consists of three major elements: Terminal Service Environment (TSE), Network Service Environment (NSE) and User Identity (UID). The concept of Always the Best Experience (ABE) is addressed as the hinge in design and development such that the user-centric services could be provided automatically and intelligently in the future diverse wireless world Based on these, we further discuss the issues on design and implementation of architecture of future wireless communication system. Requirements for architecture brought by the new features of MUSE are listed. Moreover, we also address several tradeoffs that should be taken into consideration in design. Finally, the deployment challenges for MUSE, such as reflectiveness of system, security and privacy, as well as peer-to-peer AAA are predicted.Ji Yang received PhD degree on Circuit and System, Bachelor degree on Telecommunication Engineering from Beijing University of Posts and Telecommunications (BUPT) in 2002 and 1993 respectively. Currently, he is an associate professor of BUPT, chief technical supervisor of Wireless Technology Innovation Institute, and vice manager of MTlab of Sino-Germany Software Institute. He leads the research on service and application in Future Forum in China. He also made much contribution to the China Communication Standardization Association (CCSA), including the vision of future Mobile Ubiquitous Service Environment, architecture of future B3G mobile terminal, etc. His research interests include architecture design for mobile ubiquitous networks, theory of self-organization, etc.Zhang Ping is now the professor of Beijing University of Posts and Telecommunications and director of Wireless Technology Innovation (WTI) Institute, BUPT. He has also served on the senior member of C3G Group, China MOST 863 future mobile communication FuTURE project, vice-chairman of China FuTURE Forum, and member of Vision Committee of World Wireless Research Forum(WWRF), he was vice chair of WWRF in 2005. He is also invited as the consultants for many domestic and oversea communication companies. He is very active on the international research activity on Beyond 3G area. He also participated in several European projects such as E2R and MOCCA. Until now, he has published 6 books, around 400 publications in journals and conferences in the area of telecommunications. His main research interests are theory and applications in wireless communication area. He was awarded by government, city of Beijing and Ministry of Information Industry several times for his great contribution to the industry and research activity in China.Hu Zheng is a PH.D candidate in mobile communications engineering in Wireless Technology Innovation Institute (WTI) at Beijing University of Posts and Telecommunications (BUPT). He received B.S degree from Nanjing University of Posts and Telecommunications in 2002, majoring in computer communications engineering. He currently works on serivce aspects of mobile ubiquitous communication system with focus on design and performance evaluation of interaction protocols and services in self-organized service environment.Wang Xu received the B.Tech. degree in electronic engineering from Beijing Polytechnic University (now named as Beijing University of Technology), Beijing, China, in 2002. Now he is working for his Ph.D. degree in Wireless Technology Innovation (WTI) Institute, Beijing University of Posts and Telecommunications (BUPT). His current interests include wireless communications in personal area, ad hoc networks and peer-to-peer system.Li Yinong received the BS degree major in Telecommunication Engineering in 1993 from Beijing University of Posts and Telecommunications, the MS degree and PhD degree major in Telecommunication and Electronic System in 1995 and 2003 from the Beijing University of Posts and Telecommunications. He is currently a lecture of STE (School of Telecommunication Engineering) of BUPT. His main research interests include service modeling, service composition approach, and intelligent service. In BUPT, he has given several lectures to both graduate and undergraduate students such as Information Theory, Speech Recognition, Pattern Recognition and Artificial Intelligence.     

High Speed Curve Interpolating D/A Converter

This paper presents a design of high speed curve interpolating D/A converter. We improve 8-bit data to 12-bit data, so the data resolution increases 16 times than that of original 8-bit data. The curve interpolator is developed from the linear interpolator. The simulation speed curve interpolator is about 500 MHz. The chip is fabricated by 0.8 m double-metal single poly CMOS technology. The active interpolation size of chip is 1 × 1 mm². The power dissipation is 200 mWatts at 5volt and 500 MHz for simulation result and 80 mWatts at 5 volt and 50 MHz for measurement result. The errors of interpolating result of curve interpolators are about 20 times less than that of original signal.     

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.     

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.     

Modulation instability of dispersion-shifted fiber couplers

The nonlinear coupled-mode equations are rewritten by even and odd modes. We study modulation instability (MI) of dispersion-shifted fiber couplers when either even or odd mode is launched alone by using zero-dispersion waveleng threlatively long (quasi-cw) pulses. The result shows that there are new types of MI in both the normal-dispersion and the anomalous-dispersion regimes. MI is concerned with forth-order dispersion and has no relation with third-order dispersion.Quasi-cw can be changed into pulses array under certain conditions. We can extract super short pulse from this. Furthermore,the bandwidth of gain spectra widens and its strength accretes as the input power increases.     

Experimental study of interband and intraband crosstalk in WDM networks

The impacts of interband and intraband erosstalk are studied and compared experimentally. Results show that interband crosstalk can be removed with narrow-band filters and has no influence on signal. Intraband crosstalk will result in signal eye diagram close and BER increasing. When the polarization states of signal and crosstalk align, intraband crosstalk seriously decreases signal quality. But when they misalign, it has little influence. Coherent and incoherent crosstalk are studied experimentally. Results show that coherent crosstalk is less harmful to system performance than incoherent crosstalk.