外色散腔半导体激光器选模和调谐性能的多模速率方程分析

我们对AlGaAs-GaAs DH半导体激光器(未镀增透膜)的外色散腔纵模选择和调谐性能在实验上系统地进行了研究,并从理论上进行了分析。 对具有外腔反馈的半导体激光器,其稳态多模速率方程组可以写成如下形式:     

外色散腔半导体激光器选模和调谐性能的多模速率方程分析

利用半导体激光器的外色散腔形式获得了可调谐单纵模运转,线宽小于0.1,调谐范围约110。利用多模速率方程对选模和调谐性能进行了理论分析,计算结果与实验结果基本相符。     

弱反馈光纤光栅外腔半导体激光器特性研究

分析了弱反馈光纤光栅外腔半导体激光器的工作原理 ,将反馈作用等效为光子寿命的改变 ,利用激光器简化多模速率方程理论计算了外腔激光器输出功率和边模抑制比随光栅反射率的变化关系 ,得出外腔激光器存在光栅最佳反射率的结论。并对用不同反射率光栅作外腔的半导体激光器进行了实验比较 ,对此结论进行了验证。实验中获得了边模抑制比达 2 5dB的单模输出     

光纤光栅外腔反馈的高功率半导体激光器光谱特性的研究

对光纤光栅外腔反馈的高功率半导体激光器的光谱线宽特性进行了理论与实验研究。理论分析表明，根据不同的外腔参数，激光器的线宽能被压缩或展宽。外腔反射率对光谱线宽的影响要比外腔腔长灵敏得多。实验实现了激光器的线宽由６ｎｍ到０．８ｎｍ的压缩。光纤光栅外腔反馈不仅能改善高功率半导体激光器的光谱特性，而且可提高激光器主模对次模的抑制比。     

基于全介质薄膜法布里珀罗滤光片的1550 nm可调谐外腔半导体激光器

提出并实现了一台基于单腔全介质薄膜法布里珀罗滤光片的1550 nm可调谐外腔半导体激光器。介绍了其内部的光学元件及其工作原理,随后对该半导体激光器的纵模输出特性进行了理论分析,搭建了该可调谐外腔半导体激光器。在不同的实验条件下,对该可调谐外腔半导体激光器在调谐过程中的输出波长、线宽及功率进行了实时同步测量。由所测数据总结出最佳实验条件,并得到了此条件下可调谐外腔半导体激光器的各相关参数。该可调谐外腔半导体激光器有一个线性的无跳模波长调谐区域(1547.203~1552.426)nm,一个稳定的输出光功率范围(40~50)μW,以及一个稳定的输出单纵模分布、线宽范围(100~150)MHz。该可调谐外腔半导体激光器可用于环境监测、原子与分子激光频谱研究、精确测量等领域。     

外腔半导体激光器动态模稳定性的研究

为了研究调谐过程中外腔半导体激光器的模稳定性,采用多光束干涉理论推导Littrow结构外腔半导体激光器的腔增益,并模拟其模结构。分析了光栅面和转臂不在同一平面的情形下,在光栅转动调谐时,通过匹配光栅的反馈波长变化率与外腔波长变化率,推导出最佳的初始外腔长度,并研究了动态模稳定（无跳模调谐）的范围;采用严格的耦合理论和光线变换矩阵分析了准直（耦合）透镜的位置对系统后向耦合效率的影响。结果表明,系统后向耦合效率最大可达99%,极大地压窄了中心波长为780nm半导体激光器的线宽,外腔半导体激光器的理论线宽为未加外腔时的0.96%,动态模稳定范围可达6.8nm。     

外腔半导体激光器频谱特性研究

本文在外腔半导体激光器的研究中引入了改进的速率方程组,用解析方法导出了稳态振荡条件和谱线宽度表达式,这些表达式适用于具有任意反馈量的外腔半导体激光器。理论分析与实验相符。     

SESAM锁模OP-VECSELs技术

综述了半导体可饱和吸收镜(SESAM)锁模光抽运垂直外腔面发射半导体激光器的理论,分析总结了相关实验技术手段,对SESAM锁模OP-VECSELs的最新研究成果作了介绍.     

双稳外腔半导体激光器(ECLD)模式转换的数值描述

对多模半导体激光器(LD)的速率方程组进行了数值求解,分析了光栅双稳外腔半导体激光器(ECLD)模式发生跳变时的瞬态特性,讨论了光栅转角的大小对瞬态过程的影响。结果表明,当光栅转角较小时,ECLD在功率上跳过程中,切断模(switch offmode)在熄灭前可能会产生一个窄而强的光脉冲。这一现象在下跳过程中是不存在的。且上跳时,ECLD更快地达到稳态输出。     

半导体激光器的输出模谱

利用半导体激光器多模速率方程组的隐式解析解，考虑到实际激光器的峰值增益波长与峰值谐振波长往往不一致的情况，从理论上对不同电流下半导体激光器的输出模谱进行了研究。     

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.     

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.     

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.     

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.     

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.     

Teleportation of an arbitrary unknown N-qubit entangled state under the controlling of M controllers

A new quantum protocol to teleport an arbitrary unknown N-qubit entangled state from a sender to a fixed receiver under M controllers(M < N) is proposed. The quantum resources required are M non-maximally entangled Greenberger-Home-Zeilinger (GHZ) state and N-M non-maximally entangled Einstein-Podolsky-Rosen (EPR) pairs. The sender performs N generalized Bell-state measurements on the 2N particles. Controllers take M single-particle measurement along x-axis, and the receiver needs to introduce one auxiliary two-level particle to extract quantum information probabilistically with the fidelity unit if controllers cooperate with it.     

A rigorous proof of MIMO channel capacity’s increase with antenna number

It is well known that adding more antennas at the transmitter or at the receiver may offer larger channel capacity in the multiple-input multiple-output（MIMO） communication systems. In this letter, a simple proof is presented for the fact that the channel capacity increases with an increase in the number of receiving antennas. The proof is based on the famous capacity formula of Foschini and Gans with matrix theory.     

Diode-end-pumped Nd:YVO4/LBO lasers with 4.2W continuous-wave output at 457 nm

A continuous-wave (CW) 457 nm blue laser operating at the power of 4.2 W is demonstrated by using a fiber coupled laser diode module pumped Nd: YVO4 and using LBO as the intra-cavity SHG crystal With the optimization of laser cavity and crystal parameters, the laser operates at a very high efficiency. When the pumping power is about 31 W, the output at 457nm reaches 4.2 W, and the optical to optical conversion efficiency is about 13.5% accordingly. The stability of the out putpower is better than 1.2% for 8 h continuously working.     

Call for Papers

正Wireless Body-area Networks The last decade has witnessed the convergence of three giant worlds:electronics,computer science and telecommunications.The next decade should follow this convergence in most of our activities with the generalization of sensor networks.In particular with the progress in medicine,people live longer and the aging of population will push the development of wireless personal networks