温度对石墨烯膜光纤F-P声压传感器灵敏度影响研究

石墨烯具有优异的机械、电学与光学等传感特性,有希望成为下一代可穿戴电子设备的功能敏感材料。石墨烯膜Fabry-Perot(F-P)声压传感器具有高灵敏度、小型化和抗电磁干扰等优点,但会受到温度漂移的影响。温度对传感器的影响主要体现在F-P腔长变化,引起工作点漂移,导致传感器光学灵敏度发生变化,以及改变石墨烯膜预应力。本文制备了石墨烯膜光纤F-P声压传感器探头,通过声压测试表明,温度改变了悬浮石墨烯膜的机械力学特性,在1 kHz处使其机械灵敏度由1.80 nm/Pa提高至2.44 nm/Pa。     

基于光纤光栅的光纤电流传感

将光纤光栅(FBG)封装入以超磁致伸缩材料(GMM)与永磁体构成的传感基座内形成系统核心传感部件,并将其放置于电流形成的磁场中,构成电流传感器。利用光纤迈克尔逊干涉仪(MI)对FBG波长的变化进行解调,从而获得被测交流电流信号。实验结果表明,检测幅值100 A~2000 A的交变电流时,该传感器对交变电流具有良好的线性响应。     

具有光弹性敏感元件的光学压力传感器

1.前言人们认为光弹性方法是分析应力的最满意的方法之一。该方法采用了一台测偏振的传感器,也可用于压力测量,具有较好的温度稳定性。测偏振的光学传感器采用了单模激光二极管作光源和一台全光纤光学干涉仪,在力和压力测量应用中得到了证实。结果说明,装置的灵敏度不受环境温度变化的影响。然而,干涉     

一种用于纳米计量的原子力显微镜测头的设计

介绍了我们研制的一种高精度、具有计量学意义的原子力显微镜测头.该显微测头与其它部件协同工作在50 mm×50 mm×2 mm的测量范围内实现纳米级精度的测量.测头采用光束偏转法检测探针悬臂的微小偏移,由单模保偏光纤引入半导体激光作为光源.该测头安装有3个立体反射镜作为激光干涉仪的参考镜.样品与原子力显微镜测头的相对位置可以由激光干涉仪直接读数,可溯源到米国际定义及国家基准上.激光干涉仪的布置无阿贝误差.测头采用立体光路设计,结构紧凑.测头厚度小于20 mm,质量约200 g,却实现了100 mm的反射光程.使用该测头测得与量块表面的力-距离曲线,还测得标称高度300 nm SiO2台阶样板的图像,分辨率优于0.05 nm.     

高精度位移传感器测量

利用高精度的F-P激光干涉仪,研制了一套用于高精度位移传感器的校准装置,可以校准示值误差为十几个纳米到几十个纳米的高精度位移传感器.测量原理是利用F-P激光干涉仪的灵敏度高、测量精度高等特点,将干涉仪和被测传感器同时测量放置在精密位移工作台上,通过比较激光干涉仪移动镜的位移量和被测传感器的位移量间的差异,得出被测传感器的线性,整个测量过程完全由计算机控制.该系统测量范围为0～25mm,测量不确定度为6 nm+l/2 nm(k=1).     

高精度微孔测量探头

对高精度探头的研究和发展进行了叙述,介绍了所研制的一款由一个二维角度传感器、一个弹性机构和一个自制的微球形钨探针组成的微孔测量探头。对探头的刚度和重复性分别进行了仿真验证和实验测试,结果表明:该探头在三维方向上的刚度均小于0.4 mN/μm,重复性均优于20 nm（k=2）。最后利用该探头对一个直径为420 μm的微孔进行了实际测量,测量结果验证了该探头的实用性。     

PSTM中不同探针扫描成像的模拟分析

金属纳米粒子或薄膜在可见光的激励下产生表面增强效应。尝试在光子扫描隧道显微镜(PSTM)中应用带铝的光纤探针来提高成像的分辨率和灵敏度。采用二维时域有限差分法(FDTD)模拟计算了裸光纤、尖端镀铝颗粒光纤、孔径镀铝膜光纤和全镀铝膜光纤探针的成像。结果显示,采用带铝探针后的灵敏度均比裸光纤提高两个数量级;尖端镀铝颗粒光纤探针的分辨率最好,可优于20nm;全镀铝膜和孔径镀铝膜光纤探针的分辨率分别可达到20nm和60nm。结果可供探针制备及实验参数设置参考。     

单模光纤耦合器应变特性实验研究

根据单模光纤耦合器的输出功率的比值对耦合区长度变化敏感的特点,采用螺旋测微仪对光纤耦合器的应变特性进行研究,避免了悬臂梁结构自重、梁的振动等不可控因素对测量结果的影响,有效提高了测量精度;同时对单模光纤耦合器的温度稳定性和横向抗干扰能力进行了讨论.实验证明,熔融拉锥式单模光纤耦合器不但具有应力敏感性,而且随应变呈线性单调变化,同时具有较好的温度稳定性和横向抗干扰性.     

VirtualLab Fusion对SNOM光纤探针内部光场分布的仿真

为了深入研究扫描近场光学显微镜(Scanning near-field optical microscope,SNOM)光纤探针导光特性,我们利用VirtualLab Fusion光学软件,仿真研究了光纤探针内部的光场分布.结果显示,光纤探针内部的光场分布呈固定的花样;中轴线光场具有峰值结构,其最大值位于探针出口前120nm处;这个最大峰值随着光纤外层铝层厚度的增加呈现先减小后增加,最后趋于稳定的变化,随着光源偏振态的变化呈现正弦的分布.     

高精度零件热变形量测量系统

设计了一种高精度测量零件受热变形量的实验装置.用恒温箱控制温度变化及保持温度稳定,利用电感测头对测量进行定位;同时,利用双频激光干涉仪对电感测头间距离进行精确测量,测头间的距离就是零件的受热变形量.理论分析和实验结果表明,这一系统具有较高的温度控制精度和测量精度.利用该系统对直径为50 mm的圆柱类零件在稳态均匀温度场中相同温度变化下的直径热变形量进行了5次重复性测量,其重复性误差为0.5μm.     

Development of stable monolithic wide-field Michelson interferometers

Bulk wide-field Michelson interferometers are very useful for high precision applications in remote sensing and astronomy. A stable monolithic Michelson interferometer is a key element in high precision radial velocity (RV) measurements for extrasolar planets searching and studies. Thermal stress analysis shows that matching coefficients of thermal expansion (CTEs) is a critical requirement for ensuring interferometer stability. This requirement leads to a novel design using BK7 and LAK7 materials, such that the monolithic interferometer is free from thermal distortion. The processes of design, fabrication, and testing of interferometers are described in detail. In performance evaluations, the field angle is typically 23.8° and thermal sensitivity is typically -2.6×10(-6)/°C near 550 nm, which corresponds to ～800 m/s/°C in the RV scale. Low-cost interferometer products have been commissioned in multiple RV instruments, and they are producing high stability performance over long term operations.     

Michelson interferometer for precision angle measurement

An angle-measuring technique based on an optical interferometer is reported. The technique exploits a Michelson interferometric configuration in which a right-angle prism and a glass strip are introduced into a probe beam. Simultaneous rotation of both components along an axis results in an optical path difference between the reference and the probe beams. In a second arrangement two right-angle prisms and glass strips are introduced into two beams of a Michelson interferometer. The prisms and the strips are rotated simultaneously to introduce an optical path difference between the two beams. In our arrangement, optimization of various parameters makes the net optical path difference between the two beams approximately linear for a rotation as great as +/-20 degrees . Results are simulated that show an improvement of 2-3 orders of magnitude in error and nonlinearity compared with a previously reported technique.     

Design of an interferometric system for the measurement of phasing errors in segmented mirrors

One of the new problems that has to be solved for segmented mirrors is related to periodic phasing, because for such mirrors to exhibit diffraction-limited performance the segments have to be positioned with an accuracy of a fraction of a wavelength. We describe the optical design of an instrument that measures the phasing errors (i.e., tip, tilt, and piston) between two segments under daylight conditions. Its design is based on a high-aperture white-light Michelson interferometer. It was developed at the Center for Sensors, Instruments and Systems Development (CD6) of the Technical University of Catalunya, Spain, and its final testing was carried out on the Gran Telescopio Canarias test workbench.     

White-light interferometric fiber-optic strain sensor from three-peak-wavelength broadband LED source

A white-light fiber-optic interferometer working in the spatial domain, using a special three-peak-wavelength LED as a light source and one of the two arms of the Michelson interferometer as a strain sensor, is presented. Based on the Gaussian spectrum distribution function, a simple spectrum-decomposing method is used to describe the special three-peak-wavelength LED source. Experimental and theoretical analyses show that this special three-peak-wavelength LED source can be used in white-light interferometry to simplify the problem of central-fringe identification. A white-light Michelson fiber-optic strain-sensing system that uses a tapered cantilever beam is described. Experimental results show that the strain measured by the fiber-optic sensor is linear and always less than the surrounding matrix.     

Wedge-plate shearing interferometers for collimation testing: use of a moiré technique

Various optical arrangements of a double-wedge-plate shearing interferometer are presented for checking laser beam collimation. The use of moiré fringes is found to be advantageous for setting the shear fringes parallel to the direction of shear in order to obtain a well-collimated laser beam. The experimental procedure and various details of the interferometer are discussed. A brief summary of a few methods for collimation testing that use a wedge plate is also given. The accuracies achievable with shearing interferometers that use a parallel plate, a wedge plate of small angle, a double wedge having a large wedge angle, a wedge plate of large angle along with two flat mirrors, and a wedge plate having a large angle are compared and summarized.     

A Compact Fiber-Optic Flow Velocity Sensor Based on a Twin-Core Fiber Michelson Interferometer

A novel fiber-optic flow velocity sensor based on a twin-core fiber Michelson interferometer has been proposed and demonstrated. The sensor only is a segment of twin-core fiber acting as cylinder cantilever beam. The force exerted on the cylinder by the slow flow speeds of order mm/s of the fluid with unknown velocity bends the fiber, which corresponds to the shift of the phase of the twin-core in-fiber integrated Michelson interferometer.     

Principle and analysis of the moving-optical-wedge interferometer

A new type of interferometer, the moving-optical-wedge interferometer, is presented, and its principle and properties are studied. The novel interferometer consists of one beam splitter, two flat fixed mirrors, two fixed compensating plates, one fixed optical wedge, and one moving optical wedge. The optical path difference (OPD) as a function of the displacement of the moving optical wedge from the zero path difference position is accomplished by the straight reciprocating motion of the moving optical wedge. A large physical shift of the moving optical wedge corresponds to a very short OPD value of the new interferometer if the values of the wedge angle and the refractive index of the two optical wedges are given properly. The new interferometer is not so sensitive to the velocity variation of the moving optical wedge and the mechanical disturbances compared with the Michelson interferometer, and it is very applicable to low-spectral-resolution application for any wavenumber region from the far infrared down to the ultraviolet.     

Study on the wide-angle Michelson interferometer with large air gap

A wide-angle Michelson interferometer with large air gap is proposed to effectively reduce the size of the glass arms and constraint on material. It provides a novel and practical instrument for ground based wind measurement of the upper atmosphere. The field widening conditions for the large air gap are calculated in theory. For the five spectral lines of 557.7 nm, 630.0 nm, 732.0 nm, 834.6 nm, and 865.7 nm, the optimal results under ideal condition are obtained with air gaps of 1.0 cm, 1.5 cm, and 2.0 cm, respectively. With the fixed optical path difference (OPD) of 7.495 cm, three pairs of glass arms are optimized. The pair with length of 1.5 cm for air gap, 5.765 cm for H-ZF12, and 2.956 cm for H-ZLaF54, has better effect of field widening than the other two pairs and its OPD variation is only within 0.30 wavelengths at incident angle of 3°. For developing a more practical wide-angle Michelson interferometer, the H-K9L glass with size of 4.445 cm is employed as the arm material of solid interferometer. The experiment for field of view of 3° is designed and the data processing and analysis for 60 images show the agreement between experimental results and theoretical simulation. The OPD variations are only within 0.27 wavelengths for image edge. The feasibility and practicality of the wide-angle Michelson interferometer with large air gap is proved by means of theory and experiment.     

Revisiting twin-core fiber sensors for high-temperature measurements

A twin-core fiber Michelson interferometer is evaluated as a high-temperature sensor. Although linear and reproducible operation up to 300°C is obtained, at higher temperatures (700°C) the refractive index shifts plastically and hysteresis is observed, rendering an untreated sensor head unusable. The shift is shown to be greatly reduced by an annealing process of the fiber for 10 h at 900°C, with which the linear response is preserved.