TM-polarized surface-plasma modes on metal-coated dielectriccylinders

TM-polarized surface plasma modes on a thin metallic cylindrical shell embedded in dielectric media are investigated. The dispersion characteristics of both bound modes and leaky waves are obtained for two sets of material parameters, the first corresponding to an optical fiber in which the metallic shell occupies a region between the core and the cladding and the second corresponding to a metal coated cylindrical rod in vacuum     

双峰效应光纤光栅薄膜传感器的优化设计

利用双峰谐振效应,通过在长周期光纤光栅(LPFG)包层表面涂覆一层对周围气氛敏感的薄膜,建立了一种新型薄膜传感器,其双峰谐振波长间隔随薄膜折射率的变化而变化.基于三包层光纤光栅物理模型,根据耦合模理论研究了传感器的灵敏度Sn与薄膜光学参数(折射率n3和厚度h3)和光纤光栅结构参数(光栅周期Λ、折变量σ)之间的关系.采用最优化数值方法,确定了最佳的膜层光学参数和光栅结构参数.计算表明,该类型传感器对膜层折射率的测量分辨率高达10-7.     

Experimental and Theoretical Study of Optical Antennas Formed from ZnO Nanorods Coated with a Thin Silver Film

A new design of an optical antenna formed from a ZnO nanorod coated with a thin metallic film is proposed. Arrays of ZnO nanorods coated with a thin silver film and highly oriented perpendicular to the substrate have been fabricated using carbothermal synthesis and magnetron sputtering. The problems of diffraction of electromagnetic waves by a single metal–dielectric nanooscillator located at the interface between dielectrics and on a 2D periodic array have been solved. Calculated electrodynamic characteristics of the optical nanoantennas of different lengths have been compared with experimental data. A new optical metal–dielectric diffraction grating absorbing almost 100% of the energy falling onto it at the resonance of the surface wave propagating along the metal (solid state plasma)/dielectric interface has been theoretically investigated.     

Optimization of a fiber grating film sensor based on dual peak resonance

Based on the dual peak resonance of long-period fiber grating（LPFG）, a novel film sensor is presented, in which films sensitive to the surrounding gases are coated on the cladding of the fiber grating region, and the intervals of the dual peak resonant wavelengths change with the film refractive index. According to the coupled-mode theory, a triple-clad numerical model is developed to analyze the relation between the sensitivity Sn and the thin film optical parameters （the film thickness h3 and the refractive index n3） and the fiber grating parameters （the grating period A and the core index modulation σ）. By using optimization method, the optimal film optical parameters and the grating structure parameters are obtained. Numerical simulation shows that the sensitivity of this scheme to refractive index of the films is predicted to be more than 10-7. The theoretic analysis provides straightforward foundation for the actual highly sensitive film sensors.     

两类典型光纤型SPR传感器的理论模型比较

针对基于SPR效应的两类典型光纤型传感器:传统型包层腐蚀的镀金属多模光纤传感器、新型镀金属单模光纤光栅传感器,指出其不同的SPR模型处理方法及传感特性。首先,根据传统型SPR光纤传感器的结构特点,利用平板SPR理论给出反射谱特性,同时指出并证明薄膜光学理论在平板SPR结构中与平板SPR理论的等价性。其次,针对新型SPR光纤光栅传感器结构特点,依据模式耦合思想,结合SPW模式特征,提出了光纤光栅SPR结构的理论处理方法,得到了镀金膜三包层LPFG结构的透射谱。最后,对基于SPR效应的两类典型光纤型传感器的传感特性进行了比较分析,结果表明,两类传感器对环境折射率均具有较高的分辨率,但新型光纤光栅SPR传感器的分辨率高出传统SPR光纤传感器3个数量级。     

可调谐光纤F-P线性滤波器的设计与分析

光纤滤波器在光纤通信和光纤传感领域发挥着重要的作用。本文基于光学薄膜干涉理论设计了一种用于光纤传感的可调谐F-P线性滤波器,该滤波器由两端面相对的入射光纤与出射光纤构成,两光纤端端面分别镀有反射光纤薄膜。该F-P干涉腔改善了传统F-P腔的透射率响应特性,有助于提高滤波器的线性度和线性范围。本文采用光学薄膜干涉矩阵分析法对该滤波器的透射率响应关系进行了计算与分析,并得出该FP滤波器的结构参数。设计结果表明,这种新型线性滤波器具有线性度好、线性范围宽和线性区间可调的优点。     

Light Transmittance and RF Shielding Effectiveness of a Gold Film on a Glass Substrate

Light transmittance and the Rf shielding effectiveness of a gold film on a glass substrate is investigated. The dependence of the transmittance of visible light upon the thickness or surface resistance of a gold film on a glass substrate is determined numerically by the optical properties of the gold film and glass substrate. The Rf shielding effectiveness produced in the far field over the frequency range of 100 MHz to 30 GHz by the gold film is calculated and compared with experimental data. An optimum condition is established between the light transmittance and the shielding effectiveness. The results are applicable to any transparent glass coated with any thin metallic film.     

Optical coupling between coated fibers in a compact fiber ribbon

Optical coupling between coated optical fibers in a fiber ribbon for use in compact and high-density optical cable is described. By means of a measurement system having a sensitivity of -70 dB. optical coupling of -40 dB due to a small radius fiber bend is measured for an actual fiber ribbon coated with UV-curable resin. The optical coupling mechanism is discussed using analysis models of a coated optical fiber bend. Theoretical analyses and experimental results confirm that optical coupling occurs only when the refractive indices of coating materials satisfy the condition of radiating light traveling from a fiber core to a ribbon coat.     

基于MSM结构的表面等离子体共振光纤折射率传感器

基于表面等离子体共振(SPR)效应,设计了一种基于多模-单模-多模(MSM)结构的光纤折射率传感器。采用光纤熔接的方式构成MSM结构,并且在单模光纤的表面涂覆二氧化钛/银(TiO2/Ag)复合膜构成传感单元。利用FDTD Solutions仿真分析了单模光纤长度与金属膜厚度对传感器性能的影响。结果表明:单模光纤长度越长,共振深度越深;TiO2/Ag复合膜中Ag膜厚度为50nm,TiO2膜厚度为20nm时,传感器性能最优,在1.33~1.41环境折射率范围内,传感器的灵敏度约为6 875nm/RIU。实验结果表明该光纤折射率传感器结构制作工艺简单、灵敏度高。     

海底光纤复合电缆金属护套光单元感应电势计算

运行中交变电场在海底光纤复合电缆的光单元金属护套上会产生感应电势,感应电势的大小是决定海底光纤复合电缆内采用何种光单元结构的一个主要因素。给出了金属护套光单元感应电势的计算公式,并举例计算了感应电势及感应电流。计算结果表明,一般长度的海底光纤复合电缆中金属护套光单元的感应电势较小,在安全范围内;具有径向和纵向阻水的普通金属护套光单元可用于海底光纤复合电缆中,不需要采取特殊措施。     

一种新型的高灵敏度光纤传感器的研究

为了提高传感器的灵敏度和线性度,该文提出了改变光纤的表面粗糙度和探针类型。首先通过自主搭建轮式光纤侧面抛磨系统,将光纤的一端镀一层Ag膜作为反射镜面,制备得到表面较粗糙的D型光纤探针。通过检测探针的传感特性发现,被测溶液折射率的变化会引起不同能量的吸收,由此使光功率计接收的光功率发生改变。经测试,制备的D型光纤传感器稳定性及线性度均很好,尤其是抛磨损耗为18 dB的传感器的灵敏度和线性相关系数分别高达66.02 dB/RIU和99.58%。通过对折射率的精度进行测量和计算,得到其精度高达0.000 04。结果表明,该传感结构具有广泛应用于生化传感(如新冠疫情等)及对环境污染程度进行实时监测的潜力。     

准分布式光纤表面等离子体波传感器

研究了一种基于波分复用原理的准分布式光纤表面等离子体波传感器。应用光波导理论和多层膜反射理论分析了表面等离子体波效应在同一光纤探头中连续被激励的原理及其传感模型。通过数值模拟和相应实验分别考察了蒸镀调制层对表面等离子体波共振(SPR)效果的影响,并在此基础上给出了设计的一般步骤和原则。实验结果表明,蒸镀不同厚度的Ta2O5薄膜将导致表面等离子体波共振光谱发生偏移,且随着膜厚增加而逐渐发生红移;当液体折射率n0处于1.333~1.388之间时,蒸镀有Ta2O5薄膜的光纤表面等离子体波传感器波长灵敏度达到2235 nm/RIU(Refractive Index Unit);通过在一支光纤探头上依次加工两个表面等离子体波传感区域,实现了对光波信号的连续调制。     

Temperature sensor based on etched optical fiber with a metal coating

Presented in this work is a new class of optical fiber temperature sensor, of which the heat-expansion thin film is coated on the etched fiber. It uses the method that combine thermal carving technique with chemical etching. The sensitivity of the sensor is increased and the shape size is decreased. This sensor possesses the linear temperature response and the good repeatability. These sensors can be used to measure finely the temperature which is lower than 200°c.     

Theoretical analysis of the minimization of the temperaturesensitivity of a coated optical fiber in a fiber-optic polarimeter

Closed-form solutions are used to analyze the effects of low-frequency temperature changes on coated optical fiber in a polarimeter. It is shown that coating the optical fiber with certain materials to an appropriate thickness can, theoretically, produce a zero temperature sensitivity     

扫描近场圆偏振光学显微镜

提出一种利用镀有金属薄膜的V形无孔光学探针构建的扫描近场光学显微镜,将圆偏振光注入镀有金属薄膜的V形槽内在针尖处形成近场照射光源,并利用探针收集样品表面近场光信号。理论分析表明:探针收集的近场和远场反射光之间存在一定的相位差,该相位差与探针机械结构、探针与样品的距离有关,可通过探针与样品之间的距离加以控制,因此利用偏振性器件可有效抑制远场光强。实验中,探针与样品之间的距离通过范德华力回馈控制,探针操作在接触模式,实验结果显示所测近场与远场光相位相差57,近场光学图像横向分辨率优于12 nm。     

包覆较厚介质层的金属铜球在聚焦光场中的捕获特性研究

基于核(金属)/壳(介质)微球的单光束梯度阱模型,计算了外面包覆较厚聚苯乙烯的铜微球在聚焦光场中的轴向散射力、梯度力以及合力,分析了表面被高度氧化的铜微球的轴向捕获力。不同于纯金属米氏粒子,外层包覆较厚介质材料的金属粒子在聚焦光场中容易被捕获但不能被捕获在聚焦光束的高强度区域。光学微操作实验显示:高度氧化的铜微球能被聚焦的高斯光束捕获并可以在平面内移动。理论和实验结果便于研究核壳结构金属微粒的光学特性,进一步拓展了光镊技术的应用范围。     

Theoretical model of a fiber optic remote sensor based on surface plasmon resonance for temperature detection

This paper reports on a novel design of a remote sensor for temperature detection based on surface plasmon resonance and optical fiber technology. We theoretically analyze the performance of proposed sensor under different conditions related to its constituents, i.e., optical fiber, metallic layer, sensing region, and launched light. The effect of the related parameters such as numerical aperture, fiber length, core diameter, FWHM of the Gaussian input on sensor is analyzed along with its physical explanation. The numerical results presented in this paper leads to a significant optimization of the important design parameters to achieve a high temperature detection accuracy and sensitivity of a fiber optic remote sensor.     

Polymer coating on infrared silver halide fiber for photodarkeningprotection

Infrared silver halide fibers were studied concerning the optical degradation induced by photodarkening. Infrared transmittance decreased notably in the shorter wavelength (near-infrared) region by the exposure to ultraviolet (UV) or visible light below a wavelength of ~600 nm. Black paint was tentatively coated on the unclad fiber for photodarkening protection, but the infrared transmittance of the fiber decreased heavily due to the evanescent wave absorption by the paint. To reduce this absorption loss, a fluorocarbon polymer was coated between the fiber core and the black paint. Consequently, efficient transmission was realized in the infrared region except for the 7-10-μm wavelength range, where the fluorocarbon polymer has a strong absorption band. In the 2-7-μm wavelength range, the fiber that was heated at 100°C in the polymer coating process exhibited higher transmittance than the original uncoated fiber. No optical degradation of the coated fiber was observed, even after irradiation with UV light for a period of 70 h     

Coating configuration dependency of fiber optic silver coated U-bent plasmonic sensor surfaces in concentration sensing measurements

The sensitivity of the plasmonic sensor surfaces can be enhanced significantly if the sensor region is bent to U shape. Here, an experimental verification is done to evaluate the performance variations of the U-bent plasmonic silver coated sensor surfaces with different coating orientations inside the vacuum coating chamber. The performances of uncoated, partially coated as well as fully coated optical fiber U-bent surfaces are analyzed. The results show that the coating configuration of the U-bent surfaces can affect the sensing property. A fully silver coated sensor region outperforms the other two types of sensor surfaces with better sensing capability.     

Edge-Lighting Light Guide Plate Based on Micro-Prism for Liquid Crystal Display

We designed an edge-lighting light guide plate (LGP) based on a micro-prism structure for liquid crystal display. Its top and bottom surfaces have micro-prisms, and a layer of high reflection film is coated on the bottom surface. The principle of the LGP was analyzed. The optical simulation tool ASAP was used to calculate the apex angle and height of the micro-prism on the top of the LGP, the apex angle of the micro-prism on the bottom of the LGP and the emitting angle dependent luminous flux of the LGP. By adjusting the width of micro-prisms on the bottom, the LGP achieved uniform luminance. A 12-in LGP based on a micro-prism structure as an example was designed. The results proved that the LGP based on a micro-prism structure is thin and simple with uniform luminance and high efficiency.