Transverse magnetic peak type metal-clad optical waveguide sensor

Transverse magnetic (TM) waves in a four-layer slab waveguide structure are studied for optical sensing applications. The structure consists of a semi-infinite substrate, a thin metal layer, a medium with negative permittivity and permeability as a guiding layer, and a semi-infinite layer as a cover. The proposed sensor is operated in reflection mode in which the angular position of the reflectance peak is used to detect small changes in the refractive index of the cover medium. The optimal structure parameters that correspond to the sharpest and highest peak are presented. The results reveal that for aluminum metal layer, a thickness of about 9 nm represents the optimum metal thickness. Moreover, the thickness, negative permittivity, and negative permeability of the guiding layer are found to have great impacts on the performance of the proposed optical waveguide sensor.     

Enhancement of sensitivity in optical waveguide sensors using left-handed materials

We show analytically that the sensitivity of an optical waveguide sensor can be dramatically enhanced by using a metamaterial with negative permittivity and permeability. The variation of the sensitivity of the proposed waveguide sensor with different parameters of the waveguide is studied. It is found that the sensitivity of the sensor increases with the increasing thickness of the metamaterial due to the surface polariton generation.     

Absorption Measurement Using a Leaky Waveguide Mode

We propose an optical waveguide sensor using a leaky mode for absorption measurement of liquid samples. This sensor uses a single coupling prism. A cladding layer and a waveguide layer are directly deposited on the reflecting surface of the prism. The intensity of the internally reflected beam at an appropriate incident angle is very sensitive to the imaginary part of the sample attached to the surface of the waveguide layer. The sensitivity of this sensor is controlled by the thicknesses of both cladding and waveguide layers. We studied the performance of the sensor by numerical calculation.     

Sensitivity enhancement in TE mode nonlinear planar optical waveguide sensor with metamaterial layer

The dispersion equation of the TE mode nonlinear planar optical waveguide with metamaterial layer was derived, and the sensitivity of the waveguide sensor was analyzed. The influences of structural parameters on the sensitivity of the waveguide sensor were investigated. We verify that the waveguide sensor with metamaterial layer can dramatically enhance the sensitivity compared with other waveguide sensors.     

Thin Film Waveguide Sensor for Measurement of the Absorption Coefficient of Hemoglobin Derivatives

A simple method for determining the absorption coefficient of oxyhemoglobin and deoxyhemoglobin in human blood is proposed. The method is based on a variation of the complex propagation constant of guided wave in a thin-film optical waveguide. On the waveguide layer, a serial multi-channel sample chamber is constructed to vary the interaction length between the evanescent field and the sample, and the dependence of the sensor response on the interaction length is investigated for various concentrations of two hemoglobins. The response of this sensor is linearly proportional to the interaction length and the concentration of the two hemoglobins. The attenuation constant due to the evanescent field absorption between the channels is experimentally obtained with the designed sensor, and the absorption coefficient is determined by the proposed method. The determined absorption coefficients coincided with those obtained by conventional transmission measurement.     

波导型钯(Pd)膜氢传感器数值模拟及优化

基于离子交换波导的集成型器件是氢敏传感器中很有发展潜力的一种. 传感区域由离子交换波导及其表面的金属钯膜组成, 通过有限差分法（FDM）计算了这种波导结构中的导模及表面等离子模的模场分布, 分析了其传播特性与钯膜光学常数的关系, 并结合束传播方法（BPM）对钯膜的厚度进行了优化, 使其具有最高的灵敏度.     

Optical sensors based on Fabry–Perot resonator and fringes of equal thickness structure

We propose theoretically two optical sensor structures based on Fabry–Perot resonator and fringes of equal thickness structure. Different from the conventional slab waveguide sensors in which the sample interacts with the evanescent field in the cladding layer, the proposed sensors contain the sample in the core layer. The first proposed sensor comprises a piezoelectric material as a substrate with the driving potential difference as the sensing probe for refractive index changes of the sample. The second sensor comprises fringes of equal thickness structure with the number of fringes per unit length is the probe for changes in the index of the sample. The calculations reveal that the proposed sensors have high sensitivity to changes in the refractive index of the sample.     

Fabrication and study of a metal-clad planar waveguide based biosensor

A metal-clad planar optical waveguide biosensor having five layer structure has been fabricated to study the detection of Pseudomonas and Pseudomonas-like bacteria. This waveguide is designed to increase the overlap of the evanescent field extension from the sensor face with the micro-scale biological objects in the bulk solution, to place most of the entire volume of the bacteria within the evanescent field. The results presented here leads to a significant optimization of the important design parameters to sense micro-scale biological objects. We have compared our computed results with the results obtained by similar non-metallic clad biosensor. The effect of affinity-layer refractive index on the sensitivity of these planar waveguides is also studied. We have shown this for some special cases by obtaining reflection dips at the particular angle of incidence. Our observations show that the metal-clad planar optical waveguide biosensor having higher affinity refractive index will give better sensitivity than other similar non-metallic clad biosensor. The validation of metal-clad planar optical waveguide sensor for the detection of Pseudomonas aeruginosa bacterium is also made.     

Vertical input optical ring resonator with differential operation for optical sensor

A novel waveguide ring resonator optical sensor with two resonant wavelength channels is proposed for a refractive index measurement of a test sample placed on the sensor substrate and its performance characteristics are investigated analytically and numerically. The waveguide device consists of a ring resonator, a split-ring-shaped loop waveguide, and a vertical input/output grating coupler, in which the loop waveguide acts as an additional resonator and provides another output wavelength channel of the sensor. The differential detection between the two wavelength channels enables the highly sensitive detection with temperature compensation. A numerical simulation based on a finite difference time domain (FDTD) method shows that a precise index change detection with a resolution of 10⁻⁶ can be achieved using of the proposed device.     

全光型硅微机械流量传感器初探

介绍一种新颖的全光型硅微机械流量传感器。给出该传感器结构及工作原理的理论分析，并阐述传感器样品的测试及结果。流量传感器具有带脊型波导的悬臂结构。悬梁用作器件的敏感区，而检测光束可以在脊型波导中传输。     

金属覆层保偏光纤偏振器的五层波导模型及理论分析

对金属履层保偏光纤偏振器建立了五层波导变参量物理模型,设计了自适应套孔爬山法的数值计算方法求解含多层波导本征值的复超越方程,计算结果揭示了金属覆层偏光纤偏振器的物理机制,并对器件进行了优化设计,给出了实验结果。     

InGaAsP/InP evanescent mode waveguide optical isolators and their application to InGaAsP/InP/Si hybrid evanescent optical isolators

We theoretically investigated InGaAsP/InP evanescent mode waveguide optical isolators and proposed their application to InGaAsP/InP/Si hybrid evanescent optical isolators. InGaAsP/InP evanescent optical isolators are composed of semiconductor optical amplifier (SOA) waveguides having InGaAsP multiple quantum well (MQW) active layer and upper InGaAsP waveguide layer with ferromagnetic layer. Optical isolation is obtained for evanescent optical mode in the InGaAsP waveguide layer. InGaAsP/InP/Si hybrid evanescent optical isolators are theoretically proposed based on the idea of InGaAsP/InP evanescent optical isolators. InGaAsP/InP/Si hybrid evanescent optical isolators are composed of ferromagnetic metal loaded silicon evanescent waveguides with wafer-bonded InGaAsP/InP optical gain material. The optical isolation and propagation loss are discussed with the structure of silicon evanescent waveguides, and optical isolation of 8.0 dB/mm was estimated. The concept of semiconductor evanescent mode optical isolators is feasible with InP based photonic integrated circuits and advanced silicon photonics.     

基于光波导技术的水中六价铬离子痕量检测

提出了一种基于对称金属包覆波导结构的光学传感器,利用该结构所激发的对导波层折射率虚部极其灵敏的超高阶导模为探针,结合二苯碳酰二肼与六价铬离子的特异性显色原理,对饮水中六价铬离子痕量进行探测.理论与实验结果表明,该分析方法的检测极限是1μg/L,达到了现行国际标准.该方法是一种需样少、耗时短、实时性好、稳定性高和价格低廉的在线检测方法.     

Evanescent-wave optical Cr VI sensor with a flexible fused-silica capillary as a transducer

A light-guiding, flexible fused-silica (FFS) capillary has been used in designing an optical fiber Cr VI sensor for monitoring Cr VI ions in water samples. The FFS capillary is similar to a conventional silica optical fiber in that it can guide light in the wavelength region from the UV to the near IR but different from a conventional optical fiber in that it is a tubular waveguide. The inner surface of the FFS capillary is fused silica, which one can modify to design an optical fiber chemical sensor. The FFS capillary has a cladding layer plus a protective polymer coating on its outside surface. The cladding layer ensures the ability of the FFS capillary to guide light. The protective coating increases the FFS capillary's mechanical strength and makes it robust for practical applications. Compared with conventional silica optical fibers, it is much easier and more feasible to use this FFS capillary to fabricate long-path (tens of meters to thousands of meters) evanescent-wave based chemical sensors. We describe a Cr VI sensor based on the intrinsic evanescent-wave absorption by Cr VI ions in a water sample filled inside the capillary as an example of use of a FFS capillary in chemical sensor design. This simple sensor, using a 30 m light-guiding FFS capillary as a transducer, has the capability of detecting as little as 31 parts in 10(9) of Cr VI in a water sample, which is close to the detection limit of some sophisticated, expensive analytical instruments.     

Optimization of transverse electric peak-type metal-clad waveguide sensor using double-negative materials

In a very recent work, a transverse electric peak-type metal-clad waveguide optical sensor was proposed in which a double-negative material (DNM) was used as a guiding layer. The sensor was found to exhibit a considerable angular shift of the reflectance peak for small changes in the refractive index of the analyte, due to the DNM layer. In this work, the optimization of the structure parameters is investigated to find out the most appropriate metal and its optimal thickness. Moreover, the optimal DNM layer parameters corresponding to the highest sensitivity are explored. Our calculations reveal that metals with high absolute value of the real part of the permittivity correspond to sharper peaks. Moreover, as the absolute value of the real part of both ε and μ of the DNM increases, the reflectance peak becomes sharper and the dip following the peak becomes deeper.     

Integrated optical proximity microsensor

This paper presents the design, simulation and experimental results of an integrated proximity sensor manufactured on silicon substrate. The sensor was designed for microrobotic applications like integration into a microgripper arm or detection of the position of gripper arms relative to an object. The structure is based on an SU8 polymeric optical waveguide splitted into three arms, integrated with a multielement photodetector on silicon substrate. Each element of the photodetector is a metal-semiconductor-metal (MSM) photodiode with Ti/Al Schottky interdigitated electrodes.The operation principle of this sensor consists in the light coupling in the central arm of the optical waveguide, interaction with the object (reflection) of the radiation which exits from this principal arm, the coupling of the “affected” radiation which comes back through the end of the waveguide and its splitting into three arms of the optical waveguide. From the optical waveguide, the light is coupled in photodiode and the photogenerated carriers are collected to the electrodes giving the electrical signal which is read and processed in real time.The optimal parameters of the waveguide (width, thicknesses of the core and the claddings) of the photodetector and the coupling between them were defined by simulation, using FDTD and BeamProp method (Opti FDTD software). Our microsensor can detect the position of an object in the range of 0-300 μm, as position sensor and with high precision in the range of zero to twice the wavelength, as proximity sensor.     

An optically pumped nanophotonic InP/InGaAlAs optical amplifier integrated on a SOI waveguide circuit

A small footprint integrated optical amplifier on Silicon-on-insulator is proposed in this article. By choosing to use optical pumping to drive the device, electrical contacting is avoided and the active waveguide can be made as thin as 100?nm, maximizing the optical confinement in the quantum well layers. Furthermore, the optical pumping is done through the silicon waveguide layer to optimally use the pump light. This leads to a compact device with high gain. We show 8?dB gain in pulsed regime in a 100?μm long device using a peak pump power of only 4.5?mW, while a comparable gain using an electrically pumped device would require an order of magnitude higher power consumption. This is an important step towards a CMOS-compatible optical amplifier for intra-chip optical interconnects.     

钢筋腐蚀监测的光波导传感方法原理探索

本文提出了一种用于混凝土结构钢筋腐蚀监测的光波导传感方法,该方法利用金属膜层局部取代光波导的介质包层,构成腐蚀敏感膜,从而获取金属腐蚀信息.本文依据波导理论讨论了该方法的原理,利用电化学方法在721比色皿的石英玻璃上证实了平面光波导腐蚀传感方案的可行性,并进一步用电镀方法制备出了光纤腐蚀传感器(FOCS)实验样品,取得了预期实验结果.     

Laser optical fibre heterodyne interferometer with frequency indicating of the phase shift of a light signal in an optical waveguide

Self-sustained oscillations in a laser optical fibre heterodyne interferometer are discussed; oscillations were produced by closing into a loop the single-mode optical fibres of the interferometer. Such oscillatory systems are shown to feature high-frequency stability. It is proposed to use this oscillating interferometer as a high-sensitivity sensor of external factors affecting the optical waveguide.     

Integrated waveguide sensor utilizing organic photodiodes

We present a novel optical sensor platform, combining monolithically integrated ring‐like sensor waveguides together with ring‐shaped thin‐film organic photodiodes (OPDs) on one substrate. The OPDs serve as integrated light detectors, simplifying the detection system by minimizing the number of required optical components. The waveguide structures, including a means of coupling light in and out of the waveguides, serve as sensing elements. The functionality of the concept is demonstrated by an integrated carbon dioxide sensor, utilizing absorbance as sensing principle. The integrated optical sensor platform is suitable for the parallel detection of multiple parameters in a single sensor chip using sensor arrays. (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)