长周期光纤光栅的一种温度补偿方法

研究了长周期光纤光栅的温度和应变特性,发现其透射中心波长随温度升高向长波方向漂移,随应变增大向短波方向漂移。根据这一特点,采用有机玻璃材料封装这一简单而有效的方法来补偿长周期光纤光栅中心波长随温度的漂移,补偿后的温度漂移系数减小到仅为3.7 pm/℃,有效地抑制了温度变化对中心波长漂移的影响,大大提高了用长周期光纤光栅测量液体折射率等物理量的精确度。     

一种新型光纤光栅温度补偿装置

光纤布拉格光栅(FBG)中心反射波长随温度变化会发生漂移,影响光纤激光器输出波长的稳定性和光纤光栅传感器精度.为消除光纤光栅中心波长温漂特性,设计了一种新型光纤光栅温度补偿装置,详细阐述了其工作原理,并理论推导了点胶位置的计算公式.这种新结构易调整光纤光栅粘结位置,从而可调整光纤光栅温度补偿有效长度.为验证结构设计和理论分析的正确性,搭建了实验系统,并对封装前后光纤光栅中心反射波长温度漂移率进行了测试.测试结果表明,在-30～70℃温度范围内,封装前光纤光栅中心反射波长的温度漂移率为0.0095 nm/℃,封装后中心反射波长温度漂移率仅为0.0002 nm/℃,温度稳定性提高了约40倍.     

应用于液体检测的级联长周期光纤光栅的温度减敏封装结构

研制了一种基于级联长周期光纤光栅对(LPFGP) 用作液体折射率检测的聚合物封装温 度减敏的新型结构。选用负热光系数的OE4110聚合物材料作为封装的 基底材料,封装结构中引入一个特殊的凹槽,方便 待测溶液通过通孔进入。封装后的LPFGP谐振波长温度灵敏度约10pm /℃,而相同参数的未封装的LPFGP的温度灵敏 度为120pm/℃,封装后的LPFGP大大降低了传感器谐振波长对温度变 化的灵敏度。本文的 封装装置融保护和温度补偿功能于一体,特殊的结构设计使之适用于液体折射率的检测。     

增敏型级联双参量测量的光纤传感器北大核心CSCD

旨在有效解决液体折射率检测中温度和折射率交叉敏感的问题,研制了一种增敏型光纤光栅(FBG)级联马赫-曾德尔(M-Z)结构的温度、折射率双参量测量的光纤传感器。通过多次熔接实验,调节相应参数将单模光纤(SMF)和薄芯光纤(TCF)进行拉锥熔接;然后在TCF的另一端熔接无心光纤(NCF),制备出M-Z光纤干涉仪;再在NCF末端级联上铝制毛细管增敏封装后的光纤光栅(FBG),最终完成双参量测量的光纤传感器的制备。根据M-Z干涉原理及FBG模式理论,计算了增敏FBG理论的温度灵敏度,给出了传感器的灵敏度系数矩阵与温度、折射率与透射谱的波长漂移量的理论公式。搭建了温度、折射率传感测试系统,实验结果表明:在15~85℃温度范围内,随着温度增加,该传感器的透射谱逐渐红移,封装后的FBG和M-Z结构的温度与波长偏移量线性相关系数分别为0.96323和0.91577,温度灵敏度分别为33.71 pm/℃和11.58 pm/℃;在室温下(25℃),液体折射率在1.333RIU~1.34235RIU范围内,随着折射率增加,FBG透射谱不发生偏移,M-Z透射谱逐渐蓝移,折射率与波长偏移量线性相关系数分别为0和0.98761,折射率灵敏度分别为0 nm/RIU和-493.51322 nm/RIU。该传感器可以有效提高温度、折射率的检测精度和灵敏度,可应用于环境、生物、石油化工和食品生产等领域。     

封装对长周期光纤光栅的影响

对于长周期光栅,谐振波长阶数越高,封装材料折射率对其特性的影响越大;封装材料折射率小于包层时,随封装材料折射率增大,波长减小;封装材料折射率大于包层时,波长向长波长移动1.5nm.研制了一种负热胀系数的材料用于封装光栅,使光栅波长的温度系数不大于5.1×10-3nm/K.     

磁流体包覆薄包层光纤光栅磁场传感研究

利用磁流体替代光纤布喇格光栅(FBG)的部分二氧化硅包层,制作了一种磁流体封装薄包层FBG结构的磁场传感器,研究了传感器对磁场和温度的响应特性。结果表明,在5.0～20.0mT的磁场范围内,传感器的波长灵敏度和功率灵敏度分别为34.9pm/mT和-1.063dBm/mT,波长线性响应度达到了99.2%。封装工艺未改变FBG波长随温度线性变化的特性,但受磁流体磁光效应影响,其温度灵敏度减小到9.2pm/℃。该传感器可实现磁场测量中的温度补偿,方法简单、易于实现。     

低温环境下FBG温度传感特性研究

在低温环境中,光纤光栅(Fiber Bragg Grating,FBG)材料的热膨胀系数和热光系数会发生改变,从而影响其温度传感特性。文章通过实验研究了裸光纤光栅传感器和黄铜管封装的光纤光栅传感器在低温下的温度传感特性。结果表明,在80~300 K温度范围,裸FBG温度传感器的灵敏度为6.43 pm/K,线性度为0.974,在80~230 K温度范围,温度与光纤光栅的中心波长呈现非线性关系;黄铜管封装的FBG温度传感器,在整个温度范围内灵敏度可达26 pm/K,线性度为0.996,较裸FBG温度传感器均有较大提升。对比实验表明,对光纤光栅进行封装,可以提高其温度灵敏度和线性度,改善温度传感特性。     

基于双金属结构的光纤光栅温度不敏感滤波器

为提高光纤陀螺宽谱光源的平均波长稳定性,提出了一种用60μm超短光纤光栅制作带宽11.77 nm温度不敏感滤波器的方法。利用金属材料的热膨胀系数差,设计了双金属温度补偿结构,能够随温度的升高/降低对光纤光栅压缩/拉伸,有效地补偿光纤光栅由热光效应引起的波长变化。在30～60℃的温度范围内,光纤光栅的温度灵敏度系数为0.15 pm/℃,较未补偿前降低了60倍以上。该结构具有较好的温度不敏感性,可作为光源滤波器提高光源的平均波长稳定性并有望用于高精度光纤陀螺。     

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。     

基于光纤光栅的温度不敏感光分插复用器研究

报道了一种基于光纤光栅的温度不敏感光分插复用器(OADM),该光分插复用器下载中心波长1 551.72 nm,邻道串扰小于-30 dB.采用两种不同热膨胀系数的材料对光纤光栅进行封装,在环境温度范围为-18℃～50℃时,中心波长变化0.000 4 nm/℃,温度稳定性远高于未补偿光栅指标0.01 nm/℃.     

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.     

Electronic Structure of Semiconductor Nanocrystals

This paper reviews our recent development of the use of the large-scale pseudopotential method to calculate the electronic structure of semiconductor nanocrystals, such as quantum dots and wires, which often contain tens of thousands of atoms. The calculated size-dependent exciton energies and absorption spectra of quantum dots and wires are in good agreement with experiments. We show that the electronic structure of a nanocrystal can be tuned not only by its size,but also by its shape. Finally,we show that defect properties in quantum dots can be significantly different from those in bulk semiconductors.     

Critical Stage Rule-Based Real Time Dispatch（RTD）System in Highly-Mixed-Products （HMP） FAB

An improving utilization and efficiency of critical equipments in semiconductor wafer fabrication facilities are concerned. Semiconductor manufacturing FAB is one of the most complicated and cost sensitive environments. A good dispatching tool will make big difference in equipment utilization and FAB output as a whole. The equipment in this paper is In-Line DUV Scanner. There are many factors impacting utilization and output on this equipment group. In HMP environment one of the issues is changing of reticule in this area and idle counts due to load unbalance between equipments. Here we'll introduce a rule-based RTD system which aiming at decreasing the number of recipe change and idle counts among a group of scanner equipment in a high-mixed-products FAB.     

GaAsSb/InAlAs PA DHBTs Grown by Production MBE

The epi material growth of GaAsSb based DHBTs with InAlAs emitters are investigated using a 4 × 100mm multi-wafer production Riber 49 MBE reactor fully equipped with real-time in-situ sensors including an absorption band edge spectroscope and an optical-based flux monitor. The state-of-the-art hole mobilities are obtained from 100nm thick carbon-doped GaAsSb. A Sb composition variation of less than ± 0.1 atomic percent across a 4 × 100mm platen configuration has been achieved. The large area InAlAs/GaAsSb/InP DHBT device demonstrates excellent DC characteristics,such as BVCEO＞6V and a DC current gain of 45 at 1kA/cm2 for an emitter size of 50μm × 50μm. The devices have a 40nm thick GaAsSb base with p-doping of 4. 5 × 1019cm-3 . Devices with an emitter size of 4μm × 30μm have a current gain variation less than 2% across the fully processed 100mm wafer. ft and fmax are over 50GHz,with a power efficiency of 50% ,which are comparable to standard power GaAs HBT results. These results demonstrate the potential application of GaAsSb/InP DHBT for power amplifiers and the feasibility of multi-wafer MBE for mass production of GaAsSb-based HBTs.     

Technology innovation and process integrations for sub-100nm gate patterning

This paper presents a brief overview of the Applied Centura(R)DPS(R)system,configured with silicon etch DPS Ⅱ chamber, with emphasis on discussing tuning capability for CD uniformity control. It also presents the studies of etch process chemistry and film integration impact for an overall successful gate patterning development. Discussions will focus on resolutions to key issues, such as CD uniformity, line-edge roughness, and multilayer film etching integration.     

White organic light-emitting devices based on fac tris（2- phenylpyridine） iridium sensitized 5,6,11,12-tetraphenylnap -hthacene

We have fabricated the white organic light-emitting devices （WOLEDs） based on 4,4＇ -bis（2,2 -diphenyl vinyl）-1,1＇ - biphenyl （DPVBi） and phosphorescence sensitized 5,6,11,12,-tetraphenylnaphthacene （rubrene）. The device structure is ITO/2T-NATA （20 nm）/NPBX （20 nm）/CBP： x%Ir（ppy）3：0.5% rubrene （8 nm）/NPBX （5 nm）/DPVBi （30 nm）/Alq（30 nm）/LiF（0.5 nm）/A1. In the devices, DPVBi acts as a blue light-emitting layer, the rubrene is sensitized by a phosphorescent material, fac tris （2-phenylpyridine） iridium [Ir（ppy）3], acts as a yellow light-emitting layer, and N,N＇ -bis- （1-naphthyl）- N,N＇ -diphenyl -1, 1＇ -biphenyl-4,4＇ -diamine （NPBX） acts as a hole transporting and exciton blocker layer, respectively. When the concentration of Ir （PPY）3 is 6wt%, the maximum luminance is 24960 cd/m^2 at an applied voltage of 15 V, and the maximum luminous efficiency is 5.17 cd/A at an applied voltage of 8 V.     

Complete approach to automatic identification and subpixel center location for ellipse feature

To meet the need of automatic image features extraction with high precision in visual inspection, a complete approach to automatic identification and sub-pixel center location for similar-ellipse feature is proposed. In the method, the feature area is identified automatically based on the edge attribute, and the sub-pixel center location is accomplished with the leastsquare algorithm. It shows that the method is valid, practical, and has high precision by experiment. Meanwhile this method can meet the need of instrumentation of visual inspection because of easy realization and without man-machine interaction.     

小角度扩展相关性近似算法分析

本论文提出一种在多天线MIMO信道相关性建模中小角度扩展近似理论算法,并应用于分析MIMO系统性能。分析中分别对三种不同角能量分布情况下的空间相关性研发快速近似计算法,并同时提出双模(Bi-Modal)角能量分布情况下的近似运算。通过分析这些新方法的近似效率,可以得到计算简单、复杂度低、而且符合实际的MIMO相关信道矩阵,对系统级的快速高效计算法的研究和系统级的评估以及误差分析具有重要的意义。     

Noise character analysis and the restraint of self-pulsation laser diodes

We calculate the Langevin noise sources of self-pulsation laser diodes, analyze the effects of active region noise and saturable-absorption region noise on the power fluctuation as well as period fluctuation, and propose a novel method to restrain the noise effects. A visible SIMULINK model is established to simulate the system, The results indicate that the effects of noise in absorption region can be ignored; that with the increase of DC injecting current, the noise effects enhance power jitter, and nevertheless, the period jitter is decreased; and that with external sinusoidal current modulating the self-pulsation laser diode, the noise-induced power jitter and period jitter can be suppressed greatly. This work is valuable for clock recovery in all-optical network.