长周期光纤湿度传感器特性的研究

介绍了一种可测量相对湿度的长周期光纤光栅传感器,其原理是在光纤包层外涂上聚乙烯醇(PVA)薄膜,外界湿度变化引起PVA薄膜折射率的变化,从而引起长周期光纤光栅谐振波长的改变,通过测量光纤湿度传感器长周期光纤光栅透射光谱就能得到周围环境的相对湿度.实验证明,涂覆PVA薄膜的长周期光纤光栅湿度传感器具有良好的稳定性和一系列突出优点.     

基于大偏置熔接的全光纤法布里珀罗湿度传感器

利用大偏置熔接方法在两段单模光纤(SMF)中间熔接一小段单模光纤作为支撑梁制作了一种开腔式法布里珀罗（F-P）干涉传感器。提出在干涉腔内填充一种湿度敏感型物质聚丙烯酰胺（PAM）从而形成一种高灵敏度的微型湿度计。当PAM通过吸收空气中的水蒸气而引起自身折射率发生改变,从而导致F-P干涉谱发生漂移,通过检测干涉谱的漂移量可以实现对环境相对湿度的测量。实验结果表明,这种湿度传感器在38%~78%的相对湿度范围内,在PAM折射率变化范围内其干涉谱漂移了约4 nm,漂移量与相对湿度的灵敏度约为0.1 nm/%;而在88%~98%的相对湿度范围内可实现高灵敏度的湿度测量,其干涉谱漂移了约59 nm,漂移量与相对湿度的灵敏度为5.868 nm/%。     

一种基于双模干涉的光纤折射率传感器

为实现高灵敏度的折射率测量,设计了一种基于双模干涉的光纤折射率传感器,该传感器为单模-多模-单模光纤(SMS)结构,其中单模光纤和多模光纤具有相同的直径和纤芯折射率。剥去多模光纤的包层,将其置于待测环境中,多模光纤中激发出的两个模式之间会发生干涉,当待测环境折射率发生变化时,干涉谱中的波谷会发生移动,可根据光谱中波谷的移动量来实现对折射率的测量。利用FDTD Solutions软件进行仿真模拟,得到不同折射率下的干涉谱,结果表明,位于1517.32nm的干涉谷对折射率的敏感度为1848.2nm/RIU,最小分辨率误差仅为2.74×10-5RIU。该传感器较传统光纤传感器而言,结构简单,有着高灵敏度、低分辨率误差等优点,应用前景广阔。     

基于纤芯失配多模干涉的光纤折射率传感器

基于多模干涉效应的单模-多模-单模(SMS)结构光纤折射率传感器通常需要进行包层腐蚀来提高灵敏度,而且易受环境温度影响。为克服SMS结构的这些不足,提出了一种新型的基于纤芯失配多模干涉的光纤折射率传感器,由单模光纤-色散补偿光纤-单模光纤(SMF-DCF-SMF)级联光纤布拉格光栅(FBG)构成,长度不超过100mm。对其灵敏度、线性范围和温度特性等进行了测试,实验结果显示在测量折射率为1.33～1.39的折射率液时,特征波长与折射率呈线性关系,灵敏度为232.8nm,级联的FBG具有良好的温度校准功能。     

基于光纤锥和多模渐变光纤的马赫-曾德尔干涉仪的传感特性研究

提出了一种基于光纤锥和纤芯失配光纤结构的马赫-曾德尔干涉(MZI)传感器。在距离单模光纤(SMF)锥25mm处熔接一段长30mm的多模渐变光纤(GI MMF),形成SMF-光纤锥-SMFGI MMF-SMF结构。其中,光纤锥起到增加包层模能量的作用,GI MMF为传感臂。传感器外界环境温度、折射率及应力的改变都会使传感器的纤芯基模和包层模的光程差发生改变,从而引起传感器干涉谱发生变化,通过监测干涉谱的变化可以实现对外界物理量的测量。实验研究结果表明,当环境溶液温度在30~89℃范围内变化时,传感器的温度灵敏度为78.6pm/℃,线性度为0.997;环境溶液折射率在1.333~1.394变化范围内,传感器的折射率灵敏度为81.48dB/RIU,线性度为0.989;轴向应变在0~933.3με变化范围内,传感器的应变灵敏度为0.33×10-2 dB/με,线性度为0.998。本文传感器可以实现多个物理量的同时区分测量。     

基于单模异芯光纤结构的液位传感器

提出了一种新颖的光纤液位传感器。在普通单模光纤(SMF)中间熔接一段细芯单模光纤(TCSMF),构成共轴光纤马赫曾德尔干涉仪(MZI)。液位的变化引起包层模与芯模的相位差发生改变,从而导致干涉仪的透射光谱发生改变。对传感器的工作原理和测量灵敏度及精度进行了理论分析,实验结果显示透射光谱中特征峰波长漂移量跟液位变化量呈较好的线性关系,且灵敏度随待测液体折射率的增大而增高,与理论分析结果相一致。测量得到纯水和饱和氯化钠溶液的测量灵敏度分别为0.160 nm/mm和0.228 nm/mm。该传感器采用全光纤结构,制备简单、测量精度高,可适用于折射率低于光纤包层折射率液体的高精度液位测量。     

基于腰椎扩径熔接马赫-曾德尔干涉仪的温度光纤传感器

实现了一种基于腰椎扩径熔接马赫-曾德尔(M-Z )干涉仪的温度光纤传感器。通过腰椎扩径熔接技术,分别对4.5cm 长的单模光纤(SMF)两端进行扩径,构成球形-单模-球形结构的M-Z干涉仪。该干涉仪具 有温 度敏感特性,因外界环境温度的变化会引起光纤包层模的有效折射率发生变化,从而导致干 涉光谱的变化。 通过检测同一级次干涉谷的特征波长漂移,实现对温度的测量。实验结果表明,在温度变化 范围为15～60℃ 时,干涉谱发生了明显的红移现象,传感器相应的温度灵敏度为0.068nm/℃。本文温度光纤传感器结构简单、成本低和灵敏度高,在温度检测方面具有良好的 应用前景。     

腰椎放大细芯光纤传感器实现折射率/温度同时测量的研究

根据马赫-曾德尔干涉(MZI)原理,在两段标准单模光纤(SMF)中间腰椎放大熔接长为2cm 的细芯SMF (TCSMF),构成光纤传感器。利用TCSMF的包层模、纤芯模对折射率和温度的灵敏度差异, 通过检测透 射光谱中不同级次的干涉谷的特征波长变化,结合敏感矩阵实现对折射率/温度的双参数同 时测量。实验选取 在1502.54nm波长处干涉谷的折射率和温度的 灵敏度分别为270.5171nm/RIU(其中RIU为折射率单位)和19.3 pm/℃;在1521.64nm波长处干涉谷的折射率灵 敏度为239.510nm/RIU,对温度不敏感。根据 0.01nm波长分 辨率的光谱仪(OSA),本文光纤传感器对折射率和温度的分辨率分别为3.6966×10－5 RIU 和0.518℃,也可以应用于其他参数的 测量,具有良好的应用和发展前景。     

基于模间干涉的折射率/曲率不敏感型PbS光纤温度传感器

提出了一种基于硫化铅(PbS)光纤的折射率/曲率不敏感的光纤温度传感器。该传感器制作简单,只需将一段PbS光纤无错位熔接在两段单模光纤之间即可。由于PbS光纤纤芯特殊的折射率分布,当光线由输入单模光纤进入PbS光纤时,它会在PbS光纤纤芯中激发出不同的模式,不同模式在进入输出单模光纤时将会发生干涉。当外界环境温度变化时,PbS光纤中不同模式间的光程差将会发生变化,从而引起传感器传输光谱的变化,因此可以通过检测传输光谱的变化实现对外界温度的测量。通过实验发现,PbS光纤长度为4mm时,即可得到完整的周期性干涉谱。对该传感器进行温度、折射率与曲率传感实验,可得温度灵敏度为55.45pm/℃,折射率灵敏度为2.08nm/RIU(其中RIU为单位折射率),曲率灵敏度为-0.29nm/m~(-1),说明该传感器对折射率和曲率不敏感,避免了温度测量时,折射率与曲率对其的影响。该传感器具有很小的结构尺寸,能够很好地应用在生物化学、工业生产等的温度测量场合。     

基于琼脂薄膜的微型端面光纤F-P湿度传感器

提出了一种基于琼脂薄膜的微型法布里-珀罗(F abry-Perot,F-P)光纤湿度传感器。传感器通过将标准单模光纤插入空 芯玻璃管并在玻璃管端面浸涂琼脂薄膜形成双F-P结构 。当环境相对湿度变化时,琼脂薄膜的体积和 折射率发生改变,从而引起干涉光发生波长偏移。搭建了湿度传感实验系统,对传感器的湿 度传感特性进行了表征,在50%RH—80%RH的相 对湿度范围内实现了高达1.232 nm/%RH的相对湿度测量灵敏度。该传感器尺寸紧凑、成本低、具有较好的线 性 灵敏度,且制备方式简单。     

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.     

Nanoimprint Lithography -A Next Generation High Volume Lithography Technique

IntroductionNanoimprint Lithography is a well-acknowl-edged low cost, high resolution, large area pattern-ing process. It includes the most promising methods,high-pressure hot embossing lithography (HEL) [2],UV-cured imprinting (UV-NIL) [3] and micro contactprinting (m-CP, MCP) [4]. Curing of the imprintedstructures is either done by subsequent UV-lightexposure in the case of UV-NIL or by cooling downbelow the glass transition temperature of the ther-moplastic material in case of HEL…     

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.     

Influence of PVK ： NPB hole transporting layer on the characteristics of organic light-emitting devices

A doping system consisting of NPB and PVK is employed as a composite hole transporting layer （CHTL）. By adjusting the component ratio of the doping system, a series of devices with different concentration proportion of PVK ： NPB are constracted. The result shows that doping concentration of NPB enhances the competence of hole transporting ability, and modifies the recombination region of charge as well as affects the surface morphology of doped film. Optimum device with a maximum brightness of 7852 cd/m^2 and a power efficiency of 1.75 lm/W has been obtained by choosing a concentration proportion of PVK ： NPB at 1：3.     

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.     

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.     

A method for calculating the center position of collimated light

It is a key problem to accurately calculate beam spots＇ center of measuring the warp by using a collimated laser. A new method, named double geometrical center method （DGCM）, is put forward for the first time. In this method, a plane wave perpendicularly irradiates an aperture stop, and a charge couple device （CCD） is employed to receive the diffraction-beam spots, then the geometrical centers of the fast and the second diffraction-beam spots are calculated respectively, and their mean value is regarded as the center of datum beam. In face of such adverse instances as laser intension distributing defectively, part of the image being saturated, this method can still work well. What＇s more, this method can detect whether an unacceptable error exits in the courses of image receiving, processing and calculating. The experimental results indicate the precision of this method is high.     

Preparation and Characterization of TaN ALD Precursors

High purity organic-tantalum precursors for thin film ALD TaN were synthesized and characterized.Vapor pressure and thermal stability of these precursors were studied.From the vapor pressure analysis,it was found that TBTEMT has a higher vapor pressure than any other published liquid TaN precursor,including TBTDET,TAITMATA,and IPTDET.Thermal stability of the alkyl groups on the precursors was investigated using a 1H NMR technique.The results indicated that the tertbutylimino group is the most stable group on TBTDET and TBTEMT as compared to the dialkylamido groups.Thermal stability of TaN precursors decreased in the following order:TBTDET ＞ PDMAT ＞ TBTEMT.In conclusion,precursor vapor pressure and thermal stability were tuned by making slight variations in the ligand sphere around the metal center.     

Curved crystal spectrometer for the measurement of X-ray lines from laser-produced plasmas

In order to diagnose the laser-produced plasmas, a focusing curved crystal spectrometer has been developed for measuring the X-ray lines radiated from a laser-produced plasmas. The design is based on the fact that the ray emitted from a source located at one focus of an ellipse will converge on the other focus by the reflection of the elliptical surface. The focal length and the eccentricity of the ellipse are 1350 mm and 0.9586, respectively. The spectrometer can be used to measure the X- ray lines in the wavelength range of 0.2-0.37 nm, and a LiF crystal （200） （2d = 0.4027 nm） is used as dispersive element covering Bragg angle from 30° to 67.5°. The spectrometer was tested on Shengnang- Ⅱ which can deliver laser energy of 60-80 J/pulse and the laser wavelength is 0.35 μm. Photographs of spectra including the 1 s2p ^1P1-1s^2 ^1S0 resonance line（w）, the 1s2p ^3P2-1s^2 1S0 magnetic quadrupole line（x）, the 1s2p ^3P1-1 s^2 ^1S0 intercombination lines（y）, the 1 s2p ^3S~1-1 s^2 ^1S0 forbidden line（z） in helium-like Ti Ⅹ Ⅺ and the 1 s2s2p ^2P3/2-1 s622s ^2S1/2 line（q） in lithium-like Ti Ⅹ Ⅹhave been recorded with a X-ray CCD camera. The experimental result shows that the wavelength resolution（λ/△ 2） is above 1000 and the elliptical crystal spectrometer is suitable for X-ray spectroscopy.