Evanescent-field photonic microcells and their applications in sensing

This paper reports the results of our recent studies on evanescent-field photonic microcells (PMCs) made by post-processing commercial micro-structured optical fibers and by encapsulating tapered micro/nano fibers within glass capillaries. The PMCs have a wavelength/sub-wavelength scale wave-guiding core housed within a miniature hollow compartment. The housing isolates the waveguide core from external contamination and provides a robust platform for efficient evanescent field interaction with the materials filling the compartment. The techniques for fabrication are described and the applications of the PMCs for sensing temperature, gas pressure, refractive index and mechanical acceleration are discussed.     

长周期光纤光栅的折射率梯度响应特性

通过模式耦合理论,建立了基于长周期光纤光栅(LPFG)的二层圆光波导模型;结合传输矩阵法,仿真得到了外部介质折射率呈线性分布情况下LPFG的透射谱。仿真结果表明：该结构下的LPFG透射谱特性强烈依赖于外部介质折射率梯度,当外部介质折射率梯度升高,透射谱的损耗峰深度逐渐降低,损耗峰3dB带宽逐渐增加,且增加量与折射率梯度的增加量呈较好的线性关系;当外部折射率梯度由1.1111×10-7riu/mm增加到1.1111×10-5riu/mm时,其梯度灵敏度可达到2.2×107nm·mm/riu。这一结果使折射率梯度的高灵敏度测量成为可能,为设计和制作基于LPFG的折射率梯度传感器提供了一定的理论依据,并有望用于生化反应中微小尺度下折射率呈梯度分布的液相介质的测量。     

一种用于光纤F-P传感器的微纳米级微位移工作台的研究

标定光纤F-P传感器这种微纳米级位移传感器非常困难。分析常用的微位移技术优缺点，这里提出了一种基于弹性变形原理的工作台的设计方法。建立了工作台位移变形的数学模型，对其产生位移的误差进行了理论分析。在此基础上，实际设计并开发了实验系统，用德国heidenhaiyn光栅位移传感器对光纤F-P传感器进行了标定实验。大量的标定实验证明，该微位移工作台的不确定度为0．1μm。     

An investigation of tube and rod electrode wear in micro EDM drilling

This paper studies the influence of various factors contributing to micro electrode wear during electrical discharge machining (EDM) drilling with micro rod and micro tube electrodes. In this paper, a simple method for calculating volumetric wear ratios is proposed based only on geometrical information obtained from the process. The objective of the research is to investigate the wear behaviour of electrodes and the suitability of electrode wear compensation methods. Electrode shape deformation and random variation of the volumetric wear are studied as the main factors affecting the applicability of wear compensation methods and as an indicator of the accuracy achievable with the micro EDM process.     

An all-fiber Fabry-Pérot interferometer for pressure sensing in different gaseous environments

A gas pressure sensor based on an all-fiber Fabry-Pérot interferometer (FFPI) is reported. The sensing head consists of a small section of silica rod spliced with a large offset between two single-mode fibers. The silica rod is used only as mechanical support so that an air cavity can be formed between both SMF. It is shown that the FFPI sensor is sensitive to gas pressure variation and when submitted to different gaseous environments, namely carbon dioxide, nitrogen and oxygen – sensitivities of 6.2, 4.1 and 3.6 nm/MPa, respectively, were attained. The refractive index change on nitrogen environment by means of gas pressure variation was also determined and a sensitivity of 1526 nm/RIU was obtained. The response of the sensing device to temperature variations in air was also studied and a sensitivity of −14 pm/°C was attained.     

Influence of lamination process on optical fiber sensors embedded in composite material

In the paper we present the results of our research on optical fiber sensors embedded into composite material samples. We investigate the influence of the lamination process, axial orientation of an optical fiber sensor and coating of a fiber on stress monitoring of a composite material. In the paper we present two approaches to the case of composite condition monitoring, using a polarimetric fiber optic sensor as well as fiber Bragg gratings. We also present experimental evidence that interaction between a composite material and fiber optic sensors is very significant and depends on many factors such as fiber optic axial orientation and the coating layer surrounding an optical fiber.     

基于透射式荧光型光纤生物传感器的结构设计

本文设计的基于透射式荧光型光纤生物传感器的样品反应池,采用光学技术和微流控技术、介电电泳及微/纳机械加工技术等,克服了现有同类仪器相对缺乏且多为断点测量的不足。该设计采用的微流控通道和温控系统保证生化样品在模拟生理条件下进行检测,真实地反映生物组分的特性;介电电泳将探针分子聚集到生物生物传感器的反应活性表面,保证靶标分子能探针分子的杂交,有利于微、痕量组分的富集;镜面的锥形腔体结构为聚光装置,然后将光信号耦合到光导纤维,导入光学型光纤生物传感器的检测器加工处理。该设计能缩短响应时间,提高生物传感器的检测灵敏度。     

MEMS传感器性能提高相关技术研究

在分析MEMS（微电子机械系统）传感器当前的发展现状、特点特别是在器件实用化和产品化进程中所面临的挑战后，提出了MEMS传感器技术实用化的关键－提高器件性能满足应用要求。根据研究经历举例说明改进传感器材料、结构、制作工艺和器件工作原理等具体措施对提高器件性能的作用。     

Optical characterization of elastohydrodynamic lubricated (EHL) contacts using surface plasmon resonance (SPR) effect

In this paper we report a novel optical technique based on the surface plasmon resonance (SPR) phenomenon for studying elastohydrodynamic lubricated (EHL) dimple. While it is well known that the refractive index (RI) variation in the lubricant may provide direct information on the pressure distribution inside a highly pressurized EHL dimple, one can obtain the pressure in the spectral SPR absorption curve, which corresponds to a unique color complexion in the SPR image.We have performed experiments to compare our SPR imaging technique with the one based on conventional optical interferometry. The new SPR technique provides an improvement of over 180 times in measurement accuracy. More importantly, SPR measures the RI directly and does not require any information on the lubricant film thickness. In light of these advantages, the SPR detection approach reported herein should be an attractive technique for studying EHL contacts.     

微型光机电系统

微型电子机械系统（ＭＥＭＳ）与光器件融合于一体的微型光机电系统（ＭＯＥＭＳ）成为ＭＥＭＳ研究的一个重要方向,它将会给光器件的发展带来新的飞跃,而光系统因无需力的输出,正是ＭＥＭＳ的一个理想的应用领域。本文主要介绍几种有突破性的、具有可动部件的微型光机电系统,最后提出一种新型的微光学开关。     

A Novel Opto-Mechanical System Coupled to a Spectrophotometer for Measuring Coatings on Small Size Substrates and Optical Fiber Filters

Abstract

A novel opto-mechanical system coupled to a commercial spectrophotometer using optical fibers was developed to measure optical transmittance of small samples, like filters deposited on optical fiber tips or micrometric substrates, as well as to investigate transmission uniformity of filters by surface scanning. It consists of two identical modules, reference and sample, both inserted in the chamber of the spectrophotometer. Each module was formed by an optical fiber, 200 µm core diameter and numerical aperture of 0.22, supported by adjustable positioning mounts for easing alignment. The system was validated by measuring the transmittance spectrum of a coated glass substrate with and without the opto-mechanical system, showing no significant differences between both methods. To determine the system versatility were undergone two transmittance experiments: one for a filter deposited on the tip of an optical fiber and the other by scanning the surface of a coated glass substrate. It can be concluded that the opto-mechanical system allows to measurement the transmittance of small size filters and optical fibers filters, as well as to scan over large coated surfaces to investigate coating uniformity.     

Sensitivity-optimized long-period fiber gratings for refractive index and temperature sensing

A long-period fiber grating sensor was fabricated by periodically changing the structure of single-mode fiber with an electric arc discharge technique. After the fabrication, the refractive index and temperature sensitivities were optimized by etching the cladding with hydrofluoric acid solution. The experimental results illustrate that the thinner cladding shows relatively higher refractive index and temperature sensitivities for the same order cladding mode, which are accordant with that of numerical simulation. After the long-period fiber grating was etched for 15?min, average refractive index sensitivities of 214?nm/refractive index unit (RIU) (1.3333?–?1.3931) and 1987?nm/RIU (1.4115–1.4555) were achieved. An extremely higher refractive index sensitivity of 2731?nm/RIU appears near 1.4555. By systematically studying the temperature sensing characteristic of cladding-etched long-period fiber grating in this work for the first time, the temperature sensitivity can reach as high as 144.23?pm/°C when the ambient temperature changes from 30 to 80°C. This work provides a theoretical reference for the fabrication of a high-sensitivity refractive index and temperature sensor based on arc-induced long-period fiber grating.     

反复印压作用下光学玻璃的微裂纹交互作用研究

对超声振动辅助磨削加工中BK7光学玻璃材料表面及亚表面的微裂纹扩展过程中的交互作用进行研究,使用维氏金刚石压头进行了BK7光学玻璃二次印压实验来模拟超声振动作用影响下单颗磨粒对光学玻璃的反复印压作用,同时采用界面粘结法获得了不同印压载荷及印压距离下产生的压痕及微裂纹形态特征及分布情况。实验结果表明：在相同载荷加载情况下,第二次印压产生的亚表面中位裂纹扩展最大深度受到侧向裂纹影响减小了30μm,同时侧向裂纹闭合后在光学玻璃材料表面及内部产生破碎。基于压痕断裂力学理论,分析了准静态载荷作用下光学玻璃内部应力场的分布及应力场驱动下微裂纹的扩展机制,对超声振动效应影响下微裂纹扩展的交互作用进行研究。结果表明：磨削过程中使用轴向超声振动辅助,能够有效地降低光学玻璃材料亚表面裂纹的深度,改善亚表面及表面加工质量,同时促进了工件材料的去除。     

Performance evaluation of a new taut wire system for straightness measurement of machine tools

This paper describes evaluation of a method of measuring the straightness of motion of machine tool axes using a taut wire and an optical sensor head mounted at the tool point location. In contrast to commonly used taut wire instruments, straightedges or laser-based methods, this solution combines low cost, simplicity of setup and automated data capture while achieving state of the art accuracy suitable for application on precision machine tools. A series of tests are discussed which examine the performance of the new sensing head and different wires which highlight the suitability of the taut wire properties as a straightness reference. Experimental results obtained on a production machine tool are provided with respect to the accuracy and repeatability of both the proposed taut wire system and a laser interferometer operated under the same conditions. The reference errors of wires made of different materials are compared and the wire catenary is separated from the measurement results. The uncertainty budget for taut wire and laser systems is presented and expanded uncertainty of 4 μm obtained for both. During the experiment, the method showed excellent repeatability with two standard deviations of 1.5 μm over a measuring range of 1.5 m; this performance matches that of a commercial laser interferometer-based straightness reference to within 0.1 μm.     

High sensitivity internal refractive index sensor based on a photonic crystal fiber long period grating

A high sensitivity method is reported for the measurement of the internal refractive index using a photonic crystal fiber long period grating. Long period gratings of different lengths were inscribed in photonic crystal fibers, and the air holes of the fiber had varying refractive indices. A side lobe appeared near the resonant dip through the analysis of the characteristics of transmission spectra showing variation in the refractive index. The resonant dip and its side lobe provided varying sensitivities to the internal refractive index values. The sensitivity of the side lobe was as high as 2343?nm/refractive index unit (RIU), which exceeded the value for the resonant dip (2047?nm/RIU) for refractive indices from 1.3333–1.3792. Due to the high resolution of 8.5?×?10^?6 RIU, this method offers promising applications for biological and chemical analysis in which high-precision refractive index measurements are required.     

Bragg光纤传感技术应用研究

分析了光纤光栅传感器的工作原理,介绍了成栅技术及应用前景,提出了在应用光纤光栅传感技术时解决温度、应力交叉敏感等问题的新方法.研究结果对Bragg 光纤传感器在工程技术领域具有一定的应用价值.     

Accurate measurement of the refractive index of air

An interference refractometer for absolute measurement of the refractive index of air has been developed. It is essentially based on components of a commercial Zeeman type laser interferometer system and uses a differential interferometer and a vacuum chamber with four measurement cells. The resolution and accuracy of interference phase interpolation is improved by an electronic phase meter and a detection technique which compensates for interferometer non-linearity. The system has been designed for an accuracy of a few parts in 10⁸. Experimental investigations of individual components and comparison measurements with pure gases, with Edlén's formula and with the BCR interference refractometer confirm this goal.     

锗的红外折射率精密测量

利用所研制的KGZ-Ⅱ型高精度光电折射仪,在5～10.6μm的光谱范围内,测量了由北京有色金属研究总院研制的锗的折射率,并与红外色散公式计算的结果进行了比较,分析了影响测量准确度的各项主要因素,给出了具有±3×10^-4准确度的测量结果。     

空气折射率的一种计算方法

本文利用洛伦兹-洛伦斯公式,计算了波长从近红外1694.521nm到紫外234.617nm的空气折射率,其计算精度与公式(1)相同,优于公式(2).