光学雨滴谱测量仪

光学雨滴谱测量仪能够实时监测雨滴直径分布、雨滴降落速度等气象参数,可应用于气象研究、环境监测、农业安全预警等领域。采用红外LED光源和线阵CCD,搭建了雨滴谱测量光路,并用水滴代替雨滴,演示测量了通过采样空间的水滴的直径和速度,验证了雨滴参数光学测量的可行性。实验中发现当较大雨滴紧贴CCD窗口通过采样空间时,液体透镜效应十分明显,CCD对应区域的光强增强,与通常的遮挡现象正好相反,因此在后续的程序处理中需妥善处理这类异常信号。     

Optical coatings on fiber for relative-humidity sensing applications

A fiber-optic relative-humidity （RH） sensor composed of multilayer of porous dielectric films is proposed. The transducer deposited on fiber end-face is multilayer coating consisting of nano-porous TiO2 and SiO2 films, which forms a low-fineness Fabry-Perot （F-P） filter with one of minimum reflections at about 1350- nm wavelength. The dielectric thin films realized by e-beam evaporation without ion-source assistance have columnar and porous structures, which exhibit sensitivity to RH change of environments. When the sensor is exposed to an environment of RH change from 10.9% to 92.8%, experimental results demonstrate 77.9-nm shift of characteristic wavelength.     

光纤传感技术在管道泄漏检测中的应用与进展

快速发现并定位管道泄漏对管道运输的安全至关重要,开发永久的、分布式、实时在线的管道检测传感系统是管道安全检测的重要目标.光纤传感技术具有体积小、灵敏度高、耐酸碱腐蚀、抗电磁干扰能力强、不产生电火花等优点,在管道检测中具有巨大的应用潜力.对应用于管道泄漏检测的各种光纤传感技术的原理和国内外发展现状进行了介绍,包括光纤布拉...     

Optical microfiber mode interferometer for temperature-independent refractometric sensing

We report on a functional optical microfiber mode interferometer and its applications for absolute, temperature-insensitive refractive index sensing. A standard optical fiber was tapered down to 10 μm. The central part of the taper, i.e., the microfiber, is connected to the untapered regions with two identical abrupt transitions. The transmission spectrum of our device exhibited a sinusoidal pattern due to the beating between modes. In our interferometer the period of the pattern-an absolute parameter-depends strongly on the surrounding refractive index but it is insensitive to temperature changes. The period, hence the external index, can be accurately measured by taking the fast Fourier transform (FFT) of the detected interference pattern. The measuring refractive index range of the device here proposed goes from 1.33 to 1.428 and the maximum resolution is on the order of 3.7×10(-6).     

回音壁模式光学微腔传感

回音壁模式光学微腔具有很高的品质因子和较小的模式体积,能极大地增强腔内光场与物质相互作用,已经成为超高灵敏光学传感的优异平台,也是国际学术前沿之一。文章简介了回音壁微腔传感研究现状与热点、微腔传感平台及传感机制原理;着重列举了微腔传感的部分典型应用,例如纳米尺度单个颗粒检测、温度传感、磁场传感、化学气体传感以及压力/应力等物理量传感等;最后对光学微腔传感的研究进行了展望。     

Ultrasound mediated alkaline hydrolysis of methyl benzoate--reinvestigation with crucial parameters

In the present work hydrolysis of methyl benzoate was carried out using aqueous sodium hydroxide solution at room temperature in the presence of ultrasound since otherwise the same reaction takes place at relatively high temperature. Also, the above hydrolysis reaction was investigated at a relatively larger scale with the variation in parameters influencing the emulsification process and hence the reaction rates. It has been observed that the position of ultrasound source on the liquid-liquid interface is a crucial parameter affecting the two-phase emulsification rates. The poor bulk mixing occurring in the presence of ultrasound alone with an increase in the volume of the reaction mixture and its consequent effect on the reaction kinetics has been conclusively established. These studies have shown that the use of ultrasound with mechanical stirring can result in substantial reduction in the overall power consumption, especially for reaction systems like hydrolysis that do not require very high temperatures and pressures generated by cavitation.     

Optical sensing with photonic crystal fibers

A review of optical fiber sensing demonstrations based on photonic crystal fibers is presented. The text is organized in five main sections: the first three deal with sensing approaches relying on fiber Bragg gratings, long‐period gratings and interferometric structures; the fourth one reports applications of these fibers for gas and liquid sensing; finally, the last section focuses on the exploitation of nonlinear effects in photonic crystal fibers for sensing.     

航空遥感相机光学系统设计

地球静止轨道区域凝视成像监视的目的就是为了及时发现和生成地面目标特征和参数，光学成像遥感技术是现代对地观测的一个重要手段。通常长焦距、大视场遥感系统的光学系统设计是通过提高光学成像遥感器的质量、加长焦距、提高记录介质的分辨力、提高系统的传递函数等措施提高其性能的。介绍焦距为36m，视场角达到0.75°的三反射式光学系统的设计过程，给出了设计结果。该系统实现了范围为90km×90km的瞬时对地扫描，摆动后能够对地面900km×450km区域实现凝视成像。     

Optical cavity coupled surface plasmon resonance sensing for enhanced sensitivity

A surface plasmon resonance (SPR) sensing system based on the optical cavity enhanced detection tech-nique is experimentally demonstrated. A fiber-optic laser cavity is built with a SPR sensor inside. By measuring the laser output power when the cavity is biased near the threshold point, the sensitivity, defined as the dependence of the output optical intensity on the sample variations, can be increased by about one order of magnitude compared to that of the SPR sensor alone under the intensity interrogation scheme. This could facilitate ultra-high sensitivity SPR biosensing applications. Further system miniaturization is possible by using integrated optical components and waveguide SPR sensors.     

Optical strong coupling in hybrid metal-graphene metamaterial for terahertz sensing

We propose a terahertz hybrid metamaterial composed of subwavelength metallic slits and graphene plasmonic ribbons for sensing application. This special design can cause the interaction between the plasmon resonances of the metallic slits and graphene ribbons, giving rise to a strong coupling effect and Rabi splitting. Intricate balancing in the strong coupling region can be perturbed by the carrier concentration of graphene, which is subject to the analyte on its surface. Thereby, the detection of analyte can be reflected as a frequency shift of resonance in terahertz transmission spectra. The result shows that this sensor can achieve a theoretical detection limit of 325 electrons or holes per square micrometer. Meanwhile, it also works well as a refractive index sensor with the frequency sensitivity of 485 GHz/RIU. Our results may contribute to design of ultra-micro terahertz sensors.     

Optical method for measuring structural parameters of island films

An optical method for determining characteristics of the submicron structure in island films is proposed. The method is based on the measurements of fluctuations of optical properties of a film detected when a focused laser beam is scanned over it. It is shown that the island size distribution can be determined in principle by the method proposed. Structural inhomogeneity of a Cs film on sapphire is revealed experimentally. Parameters of these inhomogeneities are measured as functions of the film thickness. The correspondence of the results of the optical method and the data of electron microscopy is tested for a In film on glass.     

Optical sensing by silicon slot-based directional couplers

A theoretical investigation of an optical liquid sensor, based on asymmetric directional coupler employing slot optical waveguides, is carried out. The sensing principle is based on the shift in the waveguide transmitted spectrum induced by analyte refractive index change. Silicon-on-insulator technology has been assumed in sensor design, and sensor modelling is carried out by using the coupled modes theory and the finite element method. The influence of geometrical parameters on the sensor characteristics has been investigated. A minimum detectable refractive index change of the order of 10^?6 can be theoretically predicted.     

传送带类问题归类分析

本文中的传送带类问题是指以皮带传送装置(传送带)为载体而构建的各类物理问题．传送带类问题丰富多彩，能够很好地再现物理知识和考查各种能力，因而值得我们分类探究．     

Optical readout method for microcantilever array sensing and its sensitivity analysis

An optical readout platform using a knife-edge filter for detecting the bending of a bimaterial microcantilever array is established, and the influence of stress-induced micromirror deformation on the optical detection sensitivity is discussed. The influence of deformation is modeled theoretically and validated experimentally. Analysis shows that the optical detection sensitivity will decrease by 50% when the mirror has a deformation of lambda/5 (lambda is the wavelength of readout light). Finally, an infrared image is obtained by the platform.     

激光回馈效应及其传感应用研究的进展

对基于激光回馈效应的传感应用研究进展进行了综述。由于激光回馈引起激光器功率波动一个条纹对应外部反射镜移动半个光波波长,功率波动深度与传统双光束干涉系统相当,基于该现象的激光回馈干涉仪与传统的干涉仪相比具有相同的相位灵敏度。但其结构简单、紧凑、易准直的特点,引起了国内外科研者浓厚的兴趣,开发了很多全新概念、经济实用的精密测量仪器。对激光回馈效应在位移测量、速度测量、振动测量、距离测量、角度测量和形貌测量中的原理进行了介绍,同时对各传感应用系统进行了评述。     

Optical time-domain reflectometry for distributed sensing of the structural strain and deformation

A unique structure of microbend optical fiber sensor (MOFS) for measuring tensile and compressive strain is described in this paper. The average measuring sensitivity for tensile strain is 35μ using 3 MOFS arrays. The repeatability and stability of MFOS are better than 18μ. The loss sensitivity of single-mode (SM) fiber and multi-mode (MM) fiber used in MOFS, as well as the relationship between the pulse width of diode laser and loss sensitivity are also studied in this paper. From these studies, some conclusions have been obtained. They are (1) the loss sensitivity and repeatability of SM fiber are better when compared to MM fiber in MOFS, and (2) the variation of pulse width of laser would only influent the signal-to-noise ratio and dynamic range, but has no contribution to loss sensitivity. Experimental results also show that loss of SM fiber highly depends on the wavelength of laser, but MM fiber has no such property. The loss of SM fiber between the wavelength of 1550 and 1310 nm is about the ratio of 6.5. Therefore, the experiments reported in this paper used a wavelength of 1310 nm to measure tensile strain and 1550 nm to measure compressive strain based on the above property of SM fiber, without changing the configuration of MOFS.     

Optical current sensing element with single medium layers for high voltage applications

The performance of a Faraday current sensing element with single medium layer coatings with potential for use at high voltage is reported, and the principle and the design parameters of the polarization-preserving, totally reflecting, single medium layer are given. The performance of the sensing element is demonstrated, showing a sensitivity of approximately 90% of the theoretically achievable maximum for an ideal case, a ratio error of 0.33% over a 7 h stability period and a 21 dB EMI immunity. Some of the advantages of this design are considered and discussed.     

Optical readout method based on a narrow-strip filter for microcantilever array sensing

An effective optical readout approach based on a narrow-strip filter is presented to detect bends of a bimaterial microcantilever focal plane array, by which light intensity of the image plane (CCD image sensor plane) can be increased and its uniformity on the image plane effectively enhanced. It reduces the noise equivalent temperature difference of the microcantilever focal plane array IR imaging system and improves uniformity of the IR images. A comparative experiment is designed to verify effectiveness. The experimental results show that the proposed method has advantages of preferable effect.     

Optical microresonator based on hollow sphere with porous wall for chemical sensing

A porous-wall hollow glass microsphere (PW-HGM) was investigated as an optical resonator for chemical vapor sensing. A single mode optical fiber taper was used to interrogate the microresonator. Adsorption of chemical molecules into the nanosized pores induced a refractive index change of the thin wall and thus a shift in its resonance spectrum. The PW-HGM resonator had shown higher vapor detection sensitivity in comparison with a solid microsphere under similar test conditions.