Broadly tunable mid-infrared VECSEL for multiple components hydrocarbon gas sensing

A new sensing platform to simultaneously identify and quantify volatile C1 to C4 alkanes in multi-component gas mixtures is presented. This setup is based on an optically pumped, broadly tunable mid-infrared vertical-external-cavity surface-emitting laser (VECSEL) developed for gas detection. The lead-chalcogenide VECSEL is the key component of the presented optical sensor. The potential of the proposed sensing setup is illustrated by experimental absorption spectra obtained from various mixtures of volatile hydrocarbons and water vapor. The sensor has a sub-ppm limit of detection for each targeted alkane in a hydrocarbon gas mixture even in the presence of a high water vapor content.     

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)     

Photonic Spin Hall Effect as a Highly Sensitive Refractive Index Sensing Platform for Glucose

This study presents an innovative refractive index (RI) sensor that measures glucose concentration by utilizing the photonic spin Hall effect (SHE) in a resonant optical tunneling effect (ROTE) structure. The ROTE structure consists of three InP layers with the high RI and two analyte layers (with a high-low-high-low-high RI distribution), in which glucose solution samples with the low RI are injected. By subjecting the InP layers to external bias-assisted light, the photonic SHE can be flexibly manipulated, enabling the modulation of the sensing performance accordingly. It is found that the transverse shift of photonic SHE presents a large variation in response to the tiny change in glucose concentrations. By optimizing the parameters (i.e., intensity or wavelength) of bias light, the sensitivity of this sensor can reach as high as 735.7 µm RIU⁻¹. Compared to traditional glucose sensors, this original work implements the novel photonic SHE with the superior sensing performance. Therefore, the proposed design shows promising potential for biomedical applications, such as medical diagnoses and drug discovery.     

Design of a highly sensitive photonic crystal waveguide platform for refractive index based biosensing

In this paper, a photonic crystal waveguide platform on silicon-on-insulator substrate is proposed in order to realize a highly sensitive refractive index based biosensor. Following the design, the analysis of the sensor structure are made by using the three dimensional Finite Difference Time Domain method. The principle of sensing is based on the change in refractive index, which in turn changes the output spectrum of the waveguide. Results show that the sensitivity of the sensor depends mainly on the geometrical properties of the defect region of the photonic crystal structure. The phenomenon is verified for various samples having refractive index ranging from 1 (air) to 1.57 (Bovine serum albumin). Further, the structure is compared with few other conventional photonic crystal waveguide designs to analyze the sensing performance. The estimated value of sensitivity of the sensor is found to be 260 nm/RIU with a detection limit of 0.001 RIU. This high sensitivity can enhance the performance of low-concentration analytes detection.     

Detection H2S mixed with natural gas using hollow-core photonic bandgap fiber

An optical fiber gas sensor using hollow-core photonic bandgap fiber as a gas cell is proposed to detect H₂S mixed with natural gas. This sensor is advantageous for eliminating instability of light source, impact of thermal zero drift, and zero shift of photoelectric device. The gas sensing probe of configuration is using two shorter pieces of hollow-core photonic bandgap fiber (HC-PBF) with the same overall length instead of one long piece of HC-PBF to improve the system response. The experimental dates indicate that a minimum detectivity of 10 ppm for the system configuration was estimated.     

Single‐mode distributed feedback laser operation with no dependence on the morphology of the gain medium

Organic distributed feedback (DFB) lasers can be useful photonic tools for biological applications where the roles of organic materials are important, because highly coherent single mode emission with broad tuning range can be obtained. However, the formulaic structures of organic lasers, and the uses of gain media as resonators themselves, are not suitable for inducing laser emission from irregular shaped gain media, such as dye‐staining cells and tissues. Here, we report a reusable photonic template comprising an exceedingly thin and discrete titanium dioxide (TiO₂) layer on a one‐dimensional (1D) quartz grating to induce single mode DFB lasing from a variety of states of optical gain media. Using the same template, the external gain media of optically thick and thin casted film, liquid, and a free‐standing thick film reveal single mode lasing with reliable performance. Numerical simulations demonstrate that the 25‐nm thick TiO₂ disconnected grating lines support a spatially confined DFB mode in the vertical direction, even under no index difference between superstrate and substrate. Additionally, not using the typical waveguide gain layer promises high sensitivity and detection limit in refractometric sensing. These results suggest that the photonic structure may serve as a versatile sensing platform for bioapplications.     

Integrated fluorescence sensor based on ring‐shaped organic photodiodes

We demonstrate a novel sensor type, which is based on the monolithic integration of luminescent optical sensor spots together with ring‐shaped thin‐film organic photodiodes on one substrate. The organic photodiodes serve as integrated fluorescence detectors, simplifying the detection system by minimizing the number of required optical components. The proposed concept enables filter‐less discrimination between excitation light and generated fluorescence light. The functionality of the concept is demonstrated by an integrated oxygen sensor, exhibiting excellent performance. The sensor spots are excited by an assembled organic light emitting diode. The integrated optical sensor platform is suitable for the parallel detection of multiple parameters. Sensor schemes for the analytical parameters carbon dioxide, temperature and ammonia, are proposed.

     

Numerical analysis of a temperature sensor based on the photonic band gap effect in a photonic crystal fiber

In this paper we investigate, by the plane wave expansion method and an analytical model, the temperature effect on the photonic band gap fiber, and we report on a numerical demonstration of a temperature sensor based on the photonic band gap (PBG) shift in a solid core photonic crystal fiber (PCF) infiltrated with a high refractive index oil. The bandwidth and the position of the central wavelength of the band gap are the parameters of interests for our temperature sensing purpose. Simulation results were found to be in excellent agreement with the refractive index scaling law and the highest sensitivity of 3.21?nm/°C was achieved, and it will be even higher than the grating based sensors written in PCFs with similar structure.     

Hollow-core photonic crystal fiber based multifunctional optical system for trapping, position sensing, and detection of fluorescent particles

We demonstrate a novel multifunctional optical system that is capable of trapping, imaging, position sensing, and fluorescence detection of micrometer-sized fluorescent test particles using hollow-core photonic crystal fiber (HC-PCF). This multifunctional optical system for trapping, position sensing, and fluorescent detection is designed such that a near-IR laser light is used to create an optical trap across a liquid-filled HC-PCF, and a 473 nm laser is employed as a source for fluorescence excitation. This proposed system and the obtained results are expected to significantly enable an efficient integrated trapping platform employing HC-PCF for diagnostic biomedical applications.     

Design of a compact photonic crystal sensor

The development of technology in photonic crystal (PC) structures has seen rapid progress. Using PCs in biosensing area may open new venues to achieve single molecule detection, and high resolution scanning. A novel PC sensor with improved performances, in terms of size, compactness and sensitivity is presented in this paper. The sensing element consists of dielectric cylinders with varying radius introduced along <01> and <10> directions of the crystal. The results show that the peak wavelength shifts to the high frequency region when only six cylinders are filled with analytes. Also, the peaks show a larger shift compared to the structure obtained using the entire PC waveguide as sensing region. The proposed sensor shows a better sensitivity to water than other analytes, where the peak wavelength tends to shift towards the low frequency region.     

导模共振效应光子晶体滤波器光谱检测稳定性的研究

由于光子晶体滤波器带宽窄和高灵敏度的特点,检测抗体含量极限可以达到ng·mL-1。可以应用于生物传感器监测生物大分子内部反应过程。一维光子晶体滤波器作为生物传感器换能元件将生物信息转化为可检测的光电信号信息,主要反应在光谱仪测得共振波峰所在波长的变化。精确测试时,检测传感系统的稳定性是首要考虑的关键因素。稳定性决定实验数据的有效性。该工作对所制备的基于导模共振效应的一维光子晶体滤波器结构进行形貌和光谱测试,介绍了实验室所搭建的实时检测传感系统。由于系统集成度、 耦合损耗等因素的影响,光谱信息出现一定的噪声信号。因此,重点提出利用Lab VIEW编程实时监控光子晶体滤波器共振波峰值随时间的变化,由光谱变化情况来反应本套检测系统的稳定性和测试数据的有效性。同时这种实时监控程序也可用来监控其他基于导模共振生物传感系统的稳定度。该检测系统由于震动,光源抖动等问题产生的共振峰值漂移为0.25 nm,通过与模拟计算结果比较可以判定系统稳定性可以达到试剂检测的要求。     

Photonic crystal microcavity as a highly sensitive platform for RI detection

In this paper, we propose a new design principle of two-dimensional photonic crystal refractive index sensors with high transmission and sensitivity simultaneously. The proposed sensor is made of two waveguide couplers and one microcavity which is obtained by varying the radius of one air hole in the center of PC structure. The microcavity is separated from the input and output waveguides by many holes of the PC. It is shown that by injecting an analyte such as gas or a liquid into a sensing hole, and thus changing its refractive index, a shift in the resonant wavelength may occur. The transmission spectra, quality factor and sensitivity of the sensor have been analyzed numerically by the finite difference time domain (FDTD) method. The sensitivity value of the sensor has been found to be 668 nm/(RIU with minimum detection limit of 0.002 RIU), which proves the ability of the structure to produce biosensor PhC.     

A quartz-enhanced photoacoustic spectroscopy sensor for measurement of water vapor concentration in the air

A compact and highly linear quartz-enhanced photoacoustic spectroscopy(QEPAS)sensor for the measurement of water vapor concentration in the air is demonstrated.A cost-effective quartz tuning fork(QTF)is used as the sharp transducer to convert light energy into an electrical signal based on the piezoelectric effect,thereby removing the need for a photodetector.The short optical path featured by the proposed sensing system leads to a decreased size.Furthermore,a pair of microresonators is applied in the absorbance detection module(ADM)for QTF signal enhancement.Compared with the system without microresonators,the detected QTF signal is increased to approximately 7-fold.Using this optimized QEPAS sensor with the proper modulation frequency and depth,we measure the water vapor concentration in the air at atmospheric pressure and room temperature.The experimental result shows that the sensor has a high sensitivity of 1.058parts-per-million.     

Silicon nitride PhC nanocavities as versatile platform for visible spectral range devices

We propose silicon nitride two-dimensional photonic crystal resonators as flexible platform to realize photonic devices based on spontaneous emission engineering of nanoemitters in the visible spectral range. The versatility of our approach is demonstrated by coupling the two dipole-like modes of a closed band gap H1 nanocavity with: (i) DNA strands marked with Cyanine 3 organic dyes, (ii) antibodies bounded to fluorescent proteins and (iii) colloidal semiconductor nanocrystals localized in the maximum of the resonant electric field. The experimental results are in good agreement with the numerical simulations, highlighting the good coupling of the nanocavities with both organic and inorganic light emitters.     

一种利用布里渊散射的光纤应变传感新方法

根据光纤中的布里渊散射附加频移与光纤所受的拉伸应变有关的特性,推导了附加频移与应变间的线性关系。在此基础上提出了利用光外差原理探测附加频移,从而实现应变探测的传感新方案,并分析了该方案能降低对激光源的线宽及频率稳定度要求之原因,给出了实验系统及实验结果。     

Study on a vapor sensor based on the optical properties of porous silicon microcavities

In this paper, we set up a sensing model of PSMs (porous silicon microcavities) by applying the Bruggeman effective medium approximation theory and the transfer matrix method. In addition, we explain in detail the adsorption characteristics of porous silicon. Finally, using an experimental setup to measure the reflectivity spectrum of PSMs when the sensor is exposed to different organic vapors, the experimental results prove that it is a feasible optical sensor for the detection of organic species. Resolution of the PSMs sensor is high, response time and resume time is short and repetition is good.      

基于太赫兹超材料的微流体折射率传感器

太赫兹生物医学是目前光谱研究领域的热点,其主要难点在于如何有效避免水分的干扰,进行液相环境下样本的灵敏分析与检测。超材料太赫兹传感器由于具有高灵敏、快速检测、痕量分析等优势,而成为太赫兹生物医学传感领域的重要研究方法。设计加工了一种基于单开口谐振环超材料的太赫兹液相传感芯片,为了有效克服水对太赫兹波的强烈吸收,利用微纳加工技术刻蚀深度为50 μm的流体通道。传感芯片整合了超材料基底与PDMS流道,在THz频段有两个位于0.771和2.129 THz的谐振峰。以水、无水乙醇作为常见化学溶剂进行传感实验,相对于空白传感器本身的THz时域谱而言,液体的加入导致时域峰的相位延迟和幅度减小。同时,由于水的折射率大于乙醇,THz透射频谱结果显示为水的频移改变量大于乙醇,且峰2大于等于峰1。上述结果表明,构建的超材料液相传感芯片是一个灵敏的折射率传感器,也证明了该传感器在测量液态样品方面的可行性。此外,利用该芯片研究了不同浓度的PBS溶液,发现水溶液中加入离子会导致谐振频率红移（以水为参考）,随着离子浓度增加,谐振频率改变量依次增加,10X PBS红移量最大,峰1为22.9 GHz,峰2为30.5 GHz。比较两个谐振峰的传感性能,峰2的传感能力更好,但是峰1对低浓度的离子溶液更加敏感。因此,构建的微流体传感器及检测体系作为一个灵敏的折射率传感器,可开发一个灵敏的无标记THz传感平台,为太赫兹生物医学研究提供新思路。     

Enhancing terahertz photonic spin Hall effect via optical Tamm state and the sensing application

The photonic spin Hall effect (PSHE), characterized by two splitting beams with opposite spins, has great potential applications in nano-photonic devices, optical sensing fields, and precision metrology. We present the significant enhancement of terahertz (THz) PSHE by taking advantage of the optical Tamm state (OTS) in InSb-distributed Bragg reflector (DBR) structure. The spin shift of reflected light can be dynamically tuned by the structural parameters (e.g. the thickness) of the InSb-DBR structure as well as the temperature, and the maximum spin shift for a horizontally polarized incident beam at 1.1 THz can reach up to 11.15 mm. Moreover, we propose a THz gas sensing device based on the enhanced PSHE via the strong excitation of OTS for the InSb-DBR structure with a superior intensity sensitivity of 5.873×10⁴ mm/RIU and good stability. This sensor exhibits two orders of magnitude improvement compared with the similar PSHE sensor based on InSb-supported THz long-range surface plasmon resonance. These findings may provide an alternative way for the enhanced PSHE and offer the opportunity for developing new optical sensing devices.     

A novel technique to measure the sucrose concentration in hydrogel sucrose solution using two dimensional photonic crystal structures

We propose a novel technique to measure the concentration of sucrose in PAm-hydrogel sucrose solution using two dimensional photonic crystal structures consists of air holes. PAm-hydrogel is an organic hydrogels, which is used as biomedical applications. The principle of measurement is based on the linear variation of photonic band gap with the change of dielectric constant of the solution infiltrated in air holes of photonic crystal structure. Plane wave expansion method is used to find the band gap and linear variation (R² = 0.9949) of photonic band gap with respect to sucrose concentration is observed. Besides this, an excellent linear variation (R² = 0.9949) of transmitted intensity of light with respect to sucrose concentration is also seen. Since the simulation is based on optical principle, it gives accurate results. This suggests the possible use of 2-D photonic crystal structure as a sucrose sensor. Experimental procedure for measuring the concentration of sucrose is also mentioned.     

二维光子晶体非对称Mach-Zehnder自准直传感器研究

基于自准直效应,通过在二维空气柱型光子晶体非对称Mach-Zehnder干涉仪长臂上设置传感区域,设计了一种自准直传感器.平面波展开法确定了入射光的自准直频率范围,时域有限差分法分析了传感器的灵敏度达到68 nm/RIU,采用单频光入射实现了传感模拟.该传感器完全依赖自准直导光,无需引入任何缺陷波导,大大降低了制作工艺要求,其大小只有十几个微米,能够满足超紧凑、高灵敏度、廉价和无标记的要求.