光束偏振对激光切割效率的影响

给出了三维激光切割理论。估计了用不同偏振方式所确定的切割效率，给出了平面平行偏振限制的物理因素。当板材厚度与切割宽度比较大时，用径向偏振光束与应用平面平行偏振以及圆偏振光束相比较，激光切割效率分别提高1.5至2倍。讨论了产生径向偏振光束的方法。     

光束的几何排布对多重径向阵列光束传输特性的影响

研究了阵列几何排布对多重径向阵列相干和非相干合成光束桶中功率（PIB）的影响。在较小的桶内阵列相干合成光束的PIB值随P增大而增大;非相干合成光束的PIB值与几何排布无关。     

径向偏振光束经三角形点阵列板衍射的偏振奇点

根据夫琅禾费衍射积分公式推导出径向偏振光束通过三角形点阵列板(TMP)衍射后的传输表达式,通过理论计算模拟并进行实验验证,得到衍射场光强分布图,衍射场光强成周期性排列。并用复Stokes场来分析径向偏振光束衍射场偏振奇点的变化规律。结果表明,衍射场的光强分布随着三角形点阵列板N值的改变而改变,偏振奇点的数目随着三角形点阵列板的N值的增大而增多。另外,光束参数(波长和光束束宽)、传输距离和三角形点阵列板的参数(三角板边长)均对偏振奇点的位置产生影响。改变三角形点阵列板的N值,伴随有偏振奇点的产生和湮灭现象。     

双曲线顶点对轴锥镜聚焦柱矢量光束的影响

基于瑞利-索末菲矢量衍射理论和振幅透过率函数,研究了轴锥镜的柱矢量光束聚焦特性。研究结果表明,径向偏振光的矢量聚焦场由径向分量及轴向分量构成,而角向偏振光的矢量聚焦场仅由角向分量构成,同时聚焦场焦深随束腰半径的增大而增加。相较理想情况,锥顶为双曲线时,焦深几乎不变,但光强因干涉效应发生振荡,其依赖于入射光的束腰半径,当径向偏振光束腰半径达到4 mm,角向偏振光束腰半径达到3.5 mm时,振荡现象消失。研究结果为轴锥镜的实际应用,以及进一步完善柱矢量光束聚焦场理论提供了参考。     

径向偏振光纯度检测及偏振态分布特性评价

光束横截面内偏振态分布均匀性是影响径向偏振光光束质量及其实际应用的关键因素。通过PBS测量法、狭缝法和S波片法三种方法对径向偏振光偏振纯度进行测量和对比,分析了径向偏振光偏振态在横截面内分布均匀性。在PBS测量法和狭缝法测量径向偏振光过程中,给出了径向偏振光纯度表达式,分别测得径向偏振光纯度为93.4%和84.1%,并引入方差公式评价径向偏振光偏振态分布均匀特性。其中PBS测量法表达径向偏振光纯度更为准确,狭缝法可以通过比较不同区域偏振度更精确地反映径向偏振光偏振态分布特性。S波片法可以使用市场现有偏振分析仪间接测量径向偏振光纯度,更适应于测量径向偏振光在放大过程中偏振态变化情况。     

矢量偏振光束的产生及其高数值孔径聚焦性质

利用石英晶体的旋光效应产生矢量偏振光束,石英晶体被分成圆心角相同的12个扇区,每个扇区设计有特定的厚度,依据晶体的旋光性质可知,在平面线偏振光入射的条件下,不同扇区产生了不同的偏振旋转,形成了空间上偏振方向不同的矢量偏振光束.进一步利用二维辛普森数值积分(ZDSC)方法计算了这种光束的高数值孔径聚焦场分布,发现此光束的聚焦性质与轴对称偏振光的极其相似,说明提出的方法可作为产生偏转角可调的轴对称偏振光的一种简单方法,而满足实际的应用需要.     

矢量光场激发三阶非线性光学效应的研究进展（特邀）

具有偏振结构分布的强激光与非线性光学材料相互作用导致了多种新颖的非线性光学效应,反映了材料的非线性光学特性,调制了光场的传播行为。笔者概述了矢量光场激发三阶非线性光学效应的研究进展。首先简要介绍了任意偏振光激发三阶非线性光学效应的理论,如非线性薛定谔方程、光束传播方程、各向同性和各向异性三阶非线性光学系数。也简要介绍了表征三阶非线性光学系数的 Z-扫描技术。在弱聚焦条件下,给出了诸如径向偏振光、杂化偏振光和柠檬型庞加莱光束这三种类型矢量光场的焦场表达式。其次,重点回顾了多种矢量光场激发的各向同性/各向异性三阶非线性光学效应,包括径向偏振光激发的各向异性非线性光学效应、杂化偏振光激发的各向同性和各向异性非线性光学效应、柠檬型庞加莱光束激发的各向同性/各向异性非线性光学效应。最后,简要讨论了矢量光场在非线性偏振旋转、光束整形、可控光场塌缩与成丝和光限幅方面的应用。     

高阶拉盖尔-高斯径向偏振光束强聚焦产生的光链

基于Richards-Wolf的矢量衍射积分公式,研究了 高阶拉盖尔-高斯径向偏振光束经过衍射光学 元件(DOE,diffractive optical elements)和高数值孔径(NA)透 镜组成的光学系统后的聚焦特性。根据数值模拟结果, 比较了相关参量的变化对深聚焦特性的影响。研究表明,入射光束经过此光学系统后,在焦 点附近产生沿 光轴方向的三维多点光俘获结构—光链,并且入射光束的相关参数和聚焦透镜的NA大小都会影响光束的聚焦特性。     

部分相干圆偏振反常涡旋光束的紧聚焦及辐射力研究

根据矢量衍射理论和部分相干理论,推导了部分相干圆偏振反常涡旋光束经过高数值孔径聚焦透镜后的光强表达式。详细讨论了入射光束参数以及聚焦透镜的数值孔径大小对光束紧聚焦特性的影响。研究结果表明:自旋方向,拓扑荷数以及数值孔径大小对光强分布有影响,相干长度以及光束阶数仅改变光强值,光束经过紧聚焦后在轴向方向上自旋角动量可以转换为轨道角动量。此外,研究了紧聚焦后光束对金属瑞利粒子的辐射力。研究表明:低阶光学参数的部分相干左旋圆偏振反常涡旋光束形成的实心光强分布可对金属瑞利粒子捕获。研究结果对部分相干涡旋光束在光镊中的应用具有理论价值。     

连续相位滤波器缩小径向偏振光束焦斑

基于矢量衍射理论,计算了径向偏振光束在焦点处光强分布。在径向偏振光束的聚焦过程中,焦斑大小主要取决于视场边缘的光线。根据这一特点,设计了以视场角正切值为自变量的连续型相位滤波函数。利用非线性规化算法,以缩小焦平面上横向宽度为目标,在不同的斯特尔比的约束条件下,优化得到一组相位滤波参数。计算结果表明,径向偏振光束通过此种相位滤波器再聚焦后,在保持相同斯特尔比的条件下,可获得更小的聚焦光斑。     

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.     

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.     

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.     

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.     

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