1．55μm超辐射发光管端面减反射膜的研究

减反射膜层折射率和厚度的精密监控是超辐射发光管的关键技术。分析了超辐射发光管端面减反射膜的四种膜系,提出了监控薄膜厚度的挡板调制、高级次过正极值法。采用该法制备超低剩余反射膜的实验表明:单面镀膜后,砷化镓基片的剩余反射率达到0.04%;管芯的反馈谐振被抑制,出现超辐射现象,峰值波长从1610nm移动到1560nm,蓝移约60nm,光谱纹波小于0.3dB。     

超辐射发光管端面AR膜的设计与制备

在中心波长1310nm的InGaAsP半导体激光器端面设计并镀制了剩余反射率小于0.03%的三层减反射膜,得到了放大自发辐射波纹小于0.5dB的超辐射发光管。     

稀土改性碳纳米管宽带吸波材料

以碳纳米管为雷达波吸收剂进行稀土掺杂后,和环氧树脂充分混合,制成复合吸波涂料并涂覆在铝板上制成吸波涂层,使用反射率扫频测量系统检测碳纳米管的吸波性能。结果表明：用适量稀土氧化物改性后,碳纳米管的吸波性能大幅提高,在8．40～16．08GHz频段内,反射率R〈-10dg,带宽迭7．68GHz,峰值R=-29．10dB,波峰在10．88GHz。反射率R〈-5dB的带宽达10．60GHz。     

干涉法测量多层透明膜系反射率

应用干涉法实现透明膜系反射率的测量。将待测膜系镀在两薄玻璃片上 ,并构成 F- P干涉仪 ,根据透射光谱的自由谱宽和干涉峰的半宽值 ,计算出膜系反射率 ,避免了光源波动对测量结果的影响。在实验中所用膜系的反射率小于 98%时 ,测量偏差小于 0 .0 0 4 %。     

一种基于载波相位的声呐阵列波达方向估计算法

针对目前各种声呐阵列波达方向估计算法复杂,系统处理速度要求较高,设计成本昂贵等问题,本文从载波信号所包含的目标方位信息出发,提出了一种新的阵列信号波达方向估计算法。该算法根据各个阵元接收信号相对延时的固定性,利用三角函数的变化关系,推导出了阵列信号的波达方向角的计算公式。仿真实验证明:当线性阵元间距为波长的1/2时,在信噪比为10 dB,波达方向角为2°～70°时,利用该算法计算所得波达方向角的精度小于0.05°;在信噪比为0 dB,波达方向角为1°～70°时,精度小于0.15°;在信噪比为-10 dB,波达方向角为1°～70°时,精度小于0.6°。     

S0951型滚动轴承振动测量仪的改进

改进后的S0951型滚动轴承振动测量仪,机械传动及加载系统更趋合理,电子测量系统的功能提高,噪声由原来的等于小于6dB降低到0dB,测振频率由原来的50Hz～10kHZ一档增加到10Hz～1kHZ、50Hz～10kHz两档,提高了测量精度和测试效率,实现了整机半自动化。附图9幅,表1个,参考文献3篇。     

反射率远场测试系统研究

搭建了基于矢量网络分析仪的反射率远场测试系统测量雷达吸波材料反射率。利用180 mm×180 mm×5 mm铝板作为标准体,检测了系统的性能指标;利用大头针测试了系统的位置精度;测试了高度300 mm的泡沫实心角锥吸波材料的反射率。实验结果表明,该反射率远场测试系统的幅度精度在1 d B内,位置误差优于5 mm,对反射率测试结果误差小于1 d B,系统测试精度小于2%。     

用光腔衰荡法测量高反射率的重复性测试

根据光腔衰荡光谱技术开展了测量镜片高反射率的研究,建立了测量实验装置,理论上给出了反射率测量的计算方法,在实验中测定了一对反射率相等的高反射腔镜的反射率,以及一块22.5°反射镜样品的反射率,所得反射率的标准偏差好于10-5。该仪器具有较高的实验重复性。     

超低透过率的测定

本文介绍了用波长为632.8nm的He—Ne激光器作为光源测量透射比小于10^-7/cm²的X光滤光片针孔透射比的方法。为了测量这样低的透过率,我们设计和安装了反射式超低透过率测定装置。用黑色玻璃作为反射式衰减元件,用光电倍增管作为接收器,用数字电压表作为读数仪表。同时,还用中性玻璃滤光片组作为透过式衰减器,也测量了超低透过率。两种方法都得出满意的结果。     

真空紫外-极紫外反射率计控制与数据采集系统

针对自行研制的真空紫外-极紫外(VUV–EUV)波段反射率计运行需要,基于LabVIEW软件构建了该反射率计控制和数据采集系统。详细介绍该系统的组成和主要硬件单元模块的控制流程与方法,并给出准直调试程序和反射率数据采集程序的架构、用户界面和数据采集方法。提出的新数据采集算法有效提高了弱信号条件下反射率测量的可靠性。利用该控制与数据采集系统,对Si基板开展了准直校准与反射率测量实验。结果表明,在7.5°～87.5°范围内直通光电流信号为20 pA时仍能获得可靠的反射率,且基于入射光监测方法的反射率测量实验结果与理论计算相符更好。除在布儒斯特角附近信号电流小于本底电流0.7 pA时,反射率重复测量误差优于1.6%。     

Changes of optical properties of retroreflector installed in LHD

This article describes changes of optical properties of retroreflectors installed on the inner wall of the vacuum vessel of the Large Helical Device. They were made of stainless steel and were used for a CO(2) laser polarimeter. The reflectivity for a CO(2) laser beam dropped up to 40% after the start of glow discharge cleanings and main plasma experiments. Then it decreased gradually. The reflectivity in a wavelength range shorter than 10 mum decreased significantly through one experimental campaign (about 4 months). On the other hand the reflectivity in a wavelength range longer than 50 mum was larger than 70%. Decrease in the reflectivity in the central region of mirrors was more significant (the reflectivity for visible beams became almost zero) than that in the edge. The distribution of the reflectivity along the radial direction is expected to be related to the shape of the retroreflector. The parallelism of the reflected beam to an incident one also deteriorated. The changes in the polarization angle and in the ellipticity of reflected light polarization were not observed from the visible to the far infrared range.     

Optical extinction monitor using cw cavity enhanced detection

We present details of an apparatus capable of measuring optical extinction (i.e., scattering and/or absorption) with high precision and sensitivity. The apparatus employs one variant of cavity enhanced detection, specifically cavity attenuated phase shift spectroscopy, using a near-confocal arrangement of two high reflectivity (R approximately 0.9999) mirrors in tandem with an enclosed cell 26 cm in length, a light emitting diode (LED), and a vacuum photodiode detector. The square wave modulated light from the LED passes through the absorption cell and is detected as a distorted wave form which is characterized by a phase shift with respect to the initial modulation. The amount of that phase shift is a function of fixed instrument properties-cell length, mirror reflectivity, and modulation frequency-and of the presence of a scatterer or absorber (air, particles, trace gases, etc.) within the cell. The specific implementation reported here employs a blue LED; the wavelength and spectral bandpass of the measurement are defined by the use of an interference filter centered at 440 nm with a 20 nm wide bandpass. The monitor is enclosed within a standard 19 in. rack-mounted instrumentation box, weighs 10 kg, and uses 70 W of electrical power including a vacuum pump. Measurements of the phase shift induced by Rayleigh scattering from several gases (which range in extinction coefficient from 0.4-32 Mm(-1)) exhibit a highly linear dependence (r(2)=0.999 97) when plotted as the co-tangent of the phase shift versus the expected extinction. Using heterodyne demodulation techniques, we demonstrate a detection limit of 0.04 Mm(-1) (4 x 10(-10) cm(-1)) (2sigma) in 10 s integration time and a base line drift of less than +/-0.1 Mm(-1) over a 24 h period. Detection limits decrease as the square root of integration time out to approximately 150 s.     

三层反射式同轴光纤束位移传感器设计

设计了用于旋转机械动静间隙测量的三层反射式同轴光纤束位移传感器.建立了光纤束传感器调制函数的数学模型,对影响传感器特性的参数,包括接收光纤纤芯半径b0、发射光纤和接收光纤的轴间距c、被测表面反射率变化等进行了仿真计算和分析,给出了系统的优化设计参数.以车削圆柱体为工件进行了动态测试,测试结果表明,该传感器有效抑制了光源波动和测量点不同对测量结果的影响,满量程范围内误差小于1%,满足了设计要求.     

光纤端面多层膜反射率的干涉测量方法研究

应用干涉法实现光纤端面多层透明膜系反射率的测量，利用镀有反射膜的待测光纤端面，构成F－P干涉仪，根据透射光谱的自由谱宽和干涉峰的半宽值，计算出膜系反射率，可直接获得光纤端面上薄膜的真实反射率，并避免了光源波动对测量结果的影响，在用反射率为92％－98．6％的膜系所进行的实验中，测量误差小于－0．09％，分析了误差来源。     

采用特殊镀膜分束器的OCT系统性能分析

基于共焦模式的OCT蒙特卡罗仿真模型,研究了在OCT系统中高散射生物组织背向散射光的反射率。仿真结果:表明对OCT成像有贡献的背向散射光强是样品臂入射光强的10^-8~10^-10,这样微弱的有用信号限制OCT系统的成像速度、探测灵敏度、信噪比和图像对比度等系统的性能。为此设计了一种带有特殊镀膜分束器的OCT系统。采用这种结构的分束器,第一,在保证入射光对生物组织无热损伤的情况下,可以尽量提高光源的输出功率,改进之后的干涉仪可以使参考光衰减4个量级,因此不会使光电探测器的输出轻易达到饱和状态。第二,大幅度减小了参考光与信号光之间的能量差距,图像干涉对比度大约提高2个数量级,即使在高速成像的情况下,仍然能够使OCT系统具备较高的成像质量。第三,这种特殊结构的干涉仪可以使样品臂的入射光最强,并将背向散射信号光因分束器反射的损失减少到最低程度,从而使系统的信噪比提高了6 dB,并通过对样品的测试可以测得系统的探测灵敏度可以提高到43 dB。     

A bench for precision measurement of rejection-filter frequency characteristics in the 2-mm wave band

The circuit and parameters of a measuring bench for precision measurement of the amplitude-frequency responses of four-pole networks in the 140-GHz band are discussed. Owing to the use of a sensitive superheterodyne receiver and radiation sources stabilized in frequency by a quartz frequency standard, the measuring bench provides a dynamic range no less than 120 dB and accuracy of frequency reading better than 1 MHz.     

气浮式转子动平衡机的结构设计

为了提高立式转子动平衡测量精度，采用气体静压球面支承技术使被测工件稳定悬浮，通过测量工件的微小偏移进行动平衡计算和校正。研制了测量装置、精密恒压供气系统和测控系统，探索了减少和消除干扰的措施。该系统克服了刚性支承摩擦力对测量精度的影响，具有很高的精度，实验表明，最小剩余不平衡度达0．8μm。     

数字化白光扫描干涉仪的研究

研究并设计实现了微形貌测量白光扫描干涉仪系统和光纤偏振耦合点监测白光扫描干涉仪系统.前者采用Mirau相移干涉形式,用压电陶瓷传感器PZT作移项器,主要用于微形貌测量,精度可达nm量级.后者采用光路补偿白光Michelson干涉形式,用格兰棱镜对偏振态进行调整控制,用移动参考臂来补偿由于耦合点所造成的光程差,光纤寄生偏振耦合测试仪的空间分辨率达到50mm,测量范围达到1km,探测灵敏度不小于-80dB(耦合模式与主模式的功率比).     

A broadband ferromagnetic resonance spectrometer to measure thin films up to 70 GHz

We report the development of a broadband ferromagnetic resonance (FMR) system operating in the frequency range from 10 MHz to 70 GHz using a closed-cycle He refrigeration system for measurements of thin films and micron/nano structures. The system is capable of carrying out measurements in frequency and field domain. Using two coplanar waveguides, it is capable of simultaneously measuring two samples in the out of plane and in plane FMR geometries. The system operates in the temperature range of 27-350 K and is sensitive to less than one atomic monolayer of a single crystal Fe film.