Microcomputer stabilization of a Fabry-Perot interferometer

Fabry-Perot interferometers typically require some form of active stabilization system for long-term operation. A stabilization system based on a microcomputer is described which is able to maintain the finesse of a plane parallel Fabry-Perot interferometer for long periods of time. The microcomputer takes the place of the multichannel analyzer, ramp generator, and stabilizer of a conventionally stabilized system. Sample data illustrating the operation of the system on the Brillouin spectrum of fused silica, with and without computer corrections, are included.     

微型膜结构全光纤珐珀干涉高温传感器

制作了一种微型膜结构的全光纤在线珐珀干涉式高温传感器。该传感器是在单模光纤端面依次熔接一段大芯径空芯光纤和一段研磨的多模光纤膜片而构成的,因此,温度引起的珐珀腔光程差改变量由空芯光纤的热膨胀和温度引起腔内压强改变从而改变膜片的扰度两部分组成,从而使相同温度变化下传感器的光程差变化量更大,分辨率更高。实验结果表明,在100～650℃,该传感器单位温度变化的光程差变化量约为1.029 nm,温度分辨率约为1.5℃,测量线性度约为0.996 7,且滞回小,重复性好。这种膜结构的全光纤珐珀干涉式高温传感器因其体积小,温度分辨率高,将在多点高温测量领域有好的应用前景。     

基于法布里-珀罗干涉仪的太赫兹波波长测试方法

太赫兹波波长的测量在其科研和实际应用中显得日益迫切和重要。阐述了由两个平行的金属网栅构成的Fabry-Perot(F-P)干涉仪测量太赫兹波波长的原理和方法,对金属网栅的参数设计原则进行了论述,从理论上分析了此方法的可行性,并根据此原理推出了计算太赫兹波线宽的公式。设计制作了测量92.9μm赫兹波的金属网栅。为太赫兹波波长测量和谱线线宽估算提供了理论参考。     

Influence of the cavity parameters on the output intensity in incoherent broadband cavity-enhanced absorption spectroscopy

The incoherent broadband cavity-enhanced absorption spectroscopy is a technique in measuring small absorptions over a broad wavelength range. The setup consists of a conventional absorption spectrometer using an incoherent lamp and a charge coupled device detector, as well as a linear optical cavity placed around the absorbing sample, which enhances the effective path length through the sample. In this work the consequences of cavity length, mirror curvature, reflectivity, different light injection geometries, and spot size of the light source on the output intensity are studied and the implications to the signal-to-noise ratio of the absorption measurement are discussed. The symmetric confocal resonator configuration is identified as a special case with optimum imaging characteristics but with higher requirements for mechanical stability. Larger spot sizes of the light source were found to be favorable in order to reduce the negative effects of aberrations on the intensity.     

基于双通道可调F-P干涉仪的机载测风激光雷达系统的鉴频器

利用双通道可调Fabry-Perot干涉仪作为机载测风激光雷达系统的鉴频器。该鉴频器可以克服现有测风雷达测速范围小的缺点,能够根据相对风速变化调整干涉仪的腔长,从而达到调整干涉仪透射谱中心频率的目的,从而间接实现测速范围动态可调,扩大测速范围的目的。采用此鉴频器可以实时测量飞行器与大气的相对风速。文中详述了测速原理和鉴频器结构,并给出机载雷达的系统参数,分析了系统的测量误差,结果表明:探测累积时间1s,测速范围为0~1000m/s时,探测高度可达30km,系统测量误差小于5m/s。     

基于白光光谱仪的绝对距离测量方法的研究

本文介绍利用一种白光光谱仪测量绝对距离和位移的方法。利用迈克耳逊干涉结构。使用光谱仪S2000。进行光谱分析。在知道光学元件的群折射率和厚度的情况下,利用均衡波长的概念就可以得出绝对距离。该方法不需要应用相位重现程序,其测量范围大大超过传统白光干涉技术的测量范围。为绝对距离的测量提供一些详尽的参考。     

非偏振分光镜对干涉式椭偏仪测量精度的影响

提出了一种新型激光外差干涉椭偏测量术用于实现纳米级精度的薄膜厚度测量。采用偏振光p和s分量透射比、反射比、反射相移、透射相移共同表征非偏振分光镜(NPBS)的退偏效应,建立了相应的误差模型,从而研究了多层介质膜NPBS的退偏效应和方位角对椭偏参数误差的影响。研究结果表明,由环境温度、入射角和光束偏振态的变化引起的NPBS退偏参数的漂移对椭偏测量精度影响很大,且无法通过标定来降低。为实现纳米级测量精度,NPBS的对准误差需要控制在0.1°以内。相对而言,用于合光的NPBS方位角误差对测量精度影响较大,NPBS所导致的膜厚测量总误差约为1.8～2.5nm,说明NPBS是马赫曾德尔干涉式椭偏仪的一个不可忽视的误差源。     

环形腔全光纤F-P干涉仪的声发射检测实验研究

提出了一种新型结构的用于声发射检测的全光纤F-P干涉仪。选用2×2光纤耦合器,将耦合器的一个入射端与一个出射端焊接相连,以耦合器代替传统的反射腔面,构成光纤环形传输腔,腔体贴附或埋入待测固体中检测声发射信号。通过理论推导和计算机仿真,确定了此结构光纤传感器的检测特性。实验以大理石板作为待测介质,对利用信号发生器驱动PZT（压电陶瓷）作为已知超声源在大理石板中产生的连续型声发射信号,及冲击波作用下大理石板中产生的突发型声发射信号进行了检测,并利用Fourier变换,得到了声发射信号的特征频率。实验结果表明,此种结构传感器能够检测材料结构中促使光纤轴向伸缩长度的量级为10-8m的声发射信号并识别其特征频率,该结构光纤传感器无需光程的匹配,适用于大尺度构件的监测,为材料结构健康检测与监控提供了一种新的方法。     

Influence of straightening conditions for a grinding wheel on the acoustic-signal intensity

Russian Engineering Research -     

基于长度可变真空腔的激光干涉空气折射率测量误差分析与补偿

为了解决基于长度可变真空腔的激光干涉空气折射率测量中透光窗片倾斜和真空腔内残余气压对测量精度的影响,本文分析了真空腔拉伸过程中透光窗片倾斜引入的误差,并提出了透光窗片倾斜误差检测和补偿方法,同时研究了真空腔内残余气压的测量和补偿方法.为了验证所提出方法的可行性,搭建了基于长度可变真空腔的激光干涉空气折射率测量系统,测量...     

Simultaneous measurement of refractive index and temperature by integrating an external Fabry-Perot cavity with a fiber Bragg grating

A fiber sensor for simultaneous measurements of refractive index and temperature based on the integration of a fiber Bragg grating (FBG) with an external Fabry-Perot (F-P) cavity is presented. The fringe contrast of the interference spectrum generated by the F-P cavity is used to determine the external refractive index, while the wavelength shift of the FBG is used to measure temperature. The result showed that the refractive index and temperature sensitivity for the integrated sensor is 8.1 × 10(-6) and 0.01006 nm/°C, respectively.     

Effect of circular cavity on maximum equivalent stress and stress intensity factor at a crack in buried pipeline

The effects of cavities on maximum equivalent stresses of buried pipelines are investigated in terms of two factors such as size and location of the underground cavities by using a finite element code. It has been found that the cavities affect maximum equivalent stresses of buried pipeline significantly in case that the diameters of cavities are larger than that of the pipeline. The variation of the stress intensity factors for a crack existing on the buried pipeline nearby cavities is also studied. The mode II stress intensity factor, K_II, for a tilt crack located at the top portion of a buried pipeline is found to be influenced significantly regardless of the location of the underground cavities.     

基底材料对石墨烯膜F-P声压传感器灵敏度的影响分析

文中以多层石墨烯膜为敏感膜片,分别制备了基于P DMS、SU-8、氧化锆的石墨烯膜F-P声压传感器,应用薄膜与基底之间吸附理论,分析了石墨烯膜与基底间吸附能相对于基底材料的杨氏模量成正向变化的趋势,并实验测试了所制备的声压传感器灵敏度.实验结果表明,制备的PDMS和SU-8基底具有较大的表面粗糙度,其虽降低了与石墨烯膜...     

反射面形状对反射式光纤位移传感器理论特性的影响

研究了反射式强度调制型光纤传感器中反射面的形状对光强调制特性的影响,推导得出了含反射面形状因子的光强调制函数.计算机仿真结果表明,若凸反射面曲率半径变大,则特性曲线的死区将变小,前坡无显著变化,后坡线性范围增大而灵敏度降低;若凹反射面曲率半径变大,则特性曲线的死区变小,前坡及后坡的线性范围减小而灵敏度增大.     

A fast beam switch for controlling the intensity in electron energy loss spectrometry

The fast deflection system described in this paper is suitable for controlling the intensity reaching the detector of a magnetic sector electron spectrometer mounted below an analytical transmission electron microscope. Amongst other things, this allows the low loss region of the spectrum to be recorded with the same electron probe conditions used to record core losses, something that is essential for high spatial resolution studies. The plate assembly restricts the width of the electron distribution reaching the viewing screen to a strip approximately 17 mm wide in the direction approximately normal to the dispersion direction of the spectrometer. The resulting deflection has no detectable effect on the FWHM of the zero-loss peak for exposure times as short as 1 micros. At incident energies up to 300 keV, positioning the deflection plates in the 35 mm camera port above the viewing chamber allows voltages of < +/- 3 kV to deflect the electrons out of the spectrometer and beyond the edge of the annular detector. When the deflection is switched on, the electrons are deflected out of the spectrometer in < 40 ns and when the deflection is switched off, the electrons return to within 10 microm of the undeflected position within 100 ns. Thus, even at an exposure time of 30 micros, the smallest time likely to be used in practice with a GATAN 666 spectrometer, < 1% of the signal in the spectrum is from electrons whose scattering conditions differ from those in the undeflected position. The performance of the deflection system is such that it will also be suitable for use with the new and much faster GATAN ENFINA spectrometer system. At incident energies up to 200 keV and possibly up to 300 keV, deflection voltages of +/- 3 kV are sufficient to deflect the electrons off a 1 k x 1 k charge coupled device (CCD) camera placed below the photographic camera. Thus the deflection system can be used as a very fast, non-mechanical shutter for such a CCD camera.     

The influence of rainfall intensity on soil loss mass from cellular confined slopes

Cellular confinement systems serve as effective solutions to any erosion control project. Small model confinements (triangular, circular, and rectangular) measuring 50, 100, and 150 mm, with a depth of 10 mm, were embedded in soil samples at slope angles of 30°, 40°, 50°, and 60°. The observed soil mass losses for the confined soil systems are much smaller. As a result, the size of confinement, rainfall intensity, and slope angle have a direct effect on the soil mass loss results. The triangular and rectangular confinement systems showed the lowest and highest soil loss masses, respectively. The slopes also failed much faster in the unconfined system than in the confined slope.     

Influence of the crosstalk on the intensity of HAADF-STEM images of quaternary semiconductor materials

The influence of the neighbouring atomic-columns in determining the composition at atomic column scale of quaternary semiconductor compounds, using simulated HAADF-STEM images is evaluated. The InAlAsSb alloy, a promising material in the photovoltaic field, is considered. We find that the so called ‘crosstalk’ effect plays an important role for the aimed compositional determination. The intensity transfer is larger from neighbouring atomic columns with higher average Z, and towards atomic columns with smaller Z. Our results show that in order to obtain precise information on the column composition, the HAADF-STEM intensities of both columns need to be taken into account simultaneously.     

Influence of a loss in the acoustic contact on the propagation of Stoneley waves near the boundary between solid half-spaces

It has been shown theoretically that a loss in the acoustic contact affects the properties of Stoneley acoustic waves at the interface between two solid half-spaces. The dispersion equation is presented in a form that allows the necessary and sufficient conditions for the existence of a boundary wave to be obtained for various combinations of parameters of the bordering media.     

紫外辐照对绝对辐射计锥腔吸收率的影响

为了研究紫外辐照对星载太阳辐射监测仪的绝对辐射计锥腔吸收率的影响,进行了实验室模拟测量实验。用相当于太阳紫外辐照总量的汞灯照射绝对辐射计的锥腔,定期用可同时测量镜、漫反射率的全半球反射比吸收率测量装置测量其吸收率,监测其随时间变化情况。实验结果表明:太阳辐射监测仪在风云三号卫星上例行工作一年接收的紫外辐射量,使其吸收率下降0.002%,最大下降0.003%,该结果同国外星上测量结果基本一致。本实验反映出紫外辐照对绝对辐射计锥腔的吸收率是有影响的,可为将来的星载太阳辐射监测仪优化、实验、测量和校正提供必要的参考。     

Influence of boundary conditions and turntable speeds on the stability of hydrostatic oil cavity

The flow, bearing, and carrying capacity of the cycloidal hydrostatic oil cavity in hydrostatic turntable systems are numerically simulated, considering the rotation speeds of a turntable from 0 to 5 m/s and different boundary conditions. The vortex effect is weakened, and the stability of the oil cavity is enhanced with the increase in lubricant viscosity. However, the increase in inlet speed, depth, and inlet radius of the oil cavity causes the vortex effect to increase and the stability of oil cavity to reduce. With the increase in the oil film thickness, the carrying capacity of the oil cavity diminishes. The oil cavity pressure increases along the direction of the motion of the turntable; it is distributed unevenly because of the rotation of the turntable. With the increase in turntable speed, the location and size of the vortex scope in the oil cavity flow field and the strength of the vortex near the entrance gradually weaken and move away from the entry. The distribution of pressure is determined by the locations of the vortex. When the vortex is close to the wall, the wall pressure increases at its location. Otherwise, the wall pressure decreases first and then increases after the center of the vortex.