Optimization of frequency characteristics for SAW device using apodization weighting method

To calibrate the tracing performance of the thirty meter telescope(TMT)tertiary mirror,for the special requirement of the TMT,the laser tracker is used to verify the motion.Firstly,the deviation is divided into two parts,namely,the repeatable error and the unrepeatable part.Then,based on the laser tracker,the mearturement and evalutation methods of the rigid body motion for the mirror are established,and the Monte Carol method is used to determine the accuracy of the mothod.Lastly,the mothod is applied to the turn table of a classical telescope and the residual error is about 4 arc second.The work of this paper will guide the next desgin and construction work of the thirty meter telescope tertiary mirror.     

Tunable thermo-optic switch based on fluid-filled photonic crystal fibers

A tunable thermo-optic intensity-modulated switch is investigated theoretically and numerically.It is based on the infiltra-tion of temperature-sensitive mixture liquids into index-guiding photonic crystal fibers(PCFs).The switching function attributes to the thermo-optic effect of the effective refractive index of the cladding.The simulation illustrates that the switch presents a tunable transition point according to the concentration of the mixture liquids,and the on-off switching functionality can be realized within a narrow temperature range of 2 oC.The switches have wide application for innovative all-in-fiber optical communication and logic devices.     

Analysis of resistive switching behaviors of vanadium oxide thin film

We demonstrated the polarization of resistive switching for Cu/VO_x/Cu memory cell. Switching behaviors of Cu/VO_x/Cu cell were tested by semiconductor device analyzer (Agilent B1500A), and the relative micro-analysis of I-V characteristics of VO_x/Cu was characterized by conductive atomic force microscope (CAFM). The I-V test results indicated that both forming and the reversible resistive switching between low resistance state (LRS) and high resistance state (HRS) can be observed under either positive or negative sweep. The CAFM images for LRS and HRS directly exhibited evidences of the formation and rupture of filaments based on positive or negative voltage. Cu/VO_x/Cu sandwiched structure exhibits a reversible resistive switching behavior and shows potential applications in the next generation nonvolatile memory field.     

光纤光热干涉气体检测技术研究进展

本文阐述光纤光热干涉气体检测的基本原理,从光纤光热相位调制的产生、动态过程、探测方法以及响应时间等方面出发,综述本研究组在光纤光热干涉气体检测方面的最新工作进展.光纤光热干涉技术具有灵敏度高、动态范围大、测量不受散射及其他损耗影响等优势,能够实现小型化、多点复用、组网及远程监测,在环境、医疗、安防等领域具有重要的应用.     

用单一倾斜光纤光栅实现曲率和温度的同时测量

基于单个倾斜光纤光栅(TFBG)提出了一种实现双参量曲率和温度同时测量的方法.研究发现,当弯曲方向与光栅栅面成一定角度时,倾斜光纤光栅的纤芯模偕振波长对弯曲不敏感而随外界温度变化线性漂移;低阶包层模谐振峰透射功率随曲率的增加而线性减小且对温度变化不敏感.由此特性提出了用单个倾斜光纤光栅的纤芯模谐振波长和低阶包层模谐振峰透射功率,分别实现对两个参量温度和曲率进行同时独立测量的传感器设计方案,该方法有望解决光纤光栅在测量中存在的温度和弯曲之间的交叉敏感问题.     

基于倾斜光纤光栅的相对湿度传感器

提出了一种基于倾斜光纤光栅(TFBG)的包层上覆盖着聚乙烯醇(PVA)的空气相对湿度传感器,成功实现了对相对湿度在20～98%RH范围内的监测。研究发现,TFBG的透射功率在20～74%RH和74～98%RH2个相对湿度区域内分别呈现不同的线性变化,敏感度分别为2.52 dBm/%RH和14.95 dBm/%RH,并且在高湿度区有更高的敏感性。     

Zn1-x MgxS薄膜的磁控溅射制备及其性能研究

利用双靶磁控溅射法,在普通石英玻璃基底上成功制备出II-VI族化合物固溶体半导体Zn1-xMgxS多晶薄膜,并用X射线能量色散谱仪(EDS)、原子力显微镜(AFM)、X射线衍射仪(XRD)、紫外-可见(UV-V is)分光光度计、荧光分光光度计(PL)等测试手段表征了多晶薄膜的成份、表面形貌、晶体结构和光学性质。结果表明:磁控溅射法制备的Zn1-xMgxS多晶薄膜具有立方和六方相混晶相结构,晶粒生长均匀,薄膜在波长小于280nm的紫外区有强烈的吸收,在可见光区紫光范围有一个强的发光峰,而且随着Mg含量的增加,强度增加,吸收边和发光峰的蓝移也增加。蓝移说明了带隙的展宽,其禁带宽度大约从3.6 eV增至4.4 eV。较高的结晶质量和发光特性显示了它是一种制作短波光电器件和紫外探测器的理想材料。     

不同包层直径的倾斜光纤光栅折射率传感特性

倾斜光纤光栅的透射谱中有纤芯模和大量的包层模,它们具有与布拉格光栅相同的温度特性.利用HF酸腐蚀的方法得到具有不同包层直径的倾斜光纤光栅,研究了其对外界折射率的传感特性.结果表明,外界环境折射率在1.333～1.4532之间变化时,同一直径倾斜光纤光栅的高阶包层模的敏感性要比低阶包层模强;随着包层直径的减小,包层模的敏感性增强,且在折射率比较高的环境中有更高的敏感性.因此,利用倾斜光纤光栅的温度特性不仅可以解决温度交叉敏感问题,而且通过小同的腐蚀程度能定制所需要的灵敏度,以实现对环境折射率的高灵敏度测量.该办法可应用于对生物和化学等高灵敏度传感领域的各种溶液进行实时监控.     

基于磁流体填充微结构光纤的温度特性研究

利用毛细现象将磁流体完全填充到六角形微结构光纤的空气孔中, 分析了磁流体填充长度、浓度对其传导特性的影响. 结合磁流体独特的热光效应, 并对一定浓度、长度下填充的光纤进行了温度特性的研究. 结果表明, 随着温度的升高, 透射谱1460 nm处磁流体的吸收峰逐渐变浅. 基于磁流体载液与表面活性剂对温度的不同敏感性, 吸收峰左右两个边沿表现出不同的温度响应; 在波长为1100–1700 nm之间透射损耗与温度变化成线性关系, 对于填充长度为10 cm的微结构光纤, 敏感度达到0.06 dB/℃, 且液体填充长度越长, 灵敏度越高. 该研究将微结构光纤与磁流体材料有机地结合起来, 并利用填充材料自身的热光特性, 实现了对透射谱的单边调谐, 将其作为热光可调谐器件、滤波器等相关可调谐光子器件在光通信、 光传感等领域将具有很大的应用潜力. 因此, 基于材料填充微结构光纤的研究可为探索新型全光纤光子器件的新技术和新结构提供有效的方法. 关键词： 微结构光纤 磁流体 热光效应 温度传感     

Effects of electrodes on resistance switching characteristics of TiO2 for flexible memory

Flexible TiO2 memory devices are fabricated on a plastic substrate at room temperature. The metal-insulator-metal (MIM) structure is grown on polyimide (PI). Several metals with different ductilities, such as Al, W, Cu and Ag, are selected as electrode. The test results show that the samples have stable resistive switching behaviors, and the electric characteristics can stay stable even after the radius of substrate is bent up to 10 mm. After 103 times of substrate bend-ing, the memory cells with W as bottom electrode on PI still show stable resistive switching characteristics and low switching voltages. The set voltage and reset voltage can be as low as 0.9 V and 0.3 V, respectively.