基于表面等离子体共振的新型超宽带微结构光纤传感器研究

基于表面等离子体共振的微结构光纤传感器具有高灵敏、免标记和实时监控等优点.如今,由于此类传感器广泛应用于食品安全控制、环境检测、生物分子分析物检测等诸多领域而受到大量研究.然而,目前所报道的绝大多数此类传感器只能应用于可见光或近中红外传感.因此,对可应用于中红外传感的表面等离子体共振微结构光纤传感器的研究是一项极具挑战性的工作.基于此,本文设计了一种可以工作在近红外和中红外区域的新型高灵敏表面等离子体共振微结构光纤传感器.传感器采用双芯单样品通道结构,该结构不仅可以消除相邻样品通道间的相互干扰和提高传感器的信噪比,还可以在超宽带波长范围内实现高灵敏检测.采用全矢量有限元法对其传感特性进行了系统的研究,研究结果表明:当待测样品折射率分布在1.423—1.513范围内时,传感器不仅可以在1.548—2.796μm的超宽带波长范围内进行工作,而且其平均灵敏度高达13964 nm/RIU.此外,传感器的最高波长灵敏度和折射率分辨率分别为17900 nm/RIU,5.59×10^–7 RIU.     

Numerical simulation of wavelength-modulated surface plasmon resonance-based fiber optic sensor

A systematically theoretical analysis of a surface plasmon resonance (SPR)-based optical fiber sensor is carried out. A three-layer mode (fiber core/gold/sample) is used to simulate the SPR-based optical fiber sensor. Several parameters including the thickness of gold layer, numerical aperture (NA) of fiber, sensing region length and fiber core diameter have been investigated to evaluate the sensitivity and measurement accuracy of sensor. A detailed explanation for the effect of these parameters on the sensor is presented to give a guideline to optimally design the SPR-based optical fiber sensor.     

侧边抛磨的U型金溅射塑料光纤等离子体共振传感器

为了测量溶液折射率变化，对塑料光纤纤芯表面的纤芯-金层-液体的3层膜结构进行研究，制作了一种使用U型结构并结合侧边抛磨方法的表面等离子体共振传感器。将截取的一段塑料光纤弯曲成为U型，并在烘箱中通过较高温度使这段光纤的曲率固定，对弯曲部分的外表面进行抛光，暴露该位置塑料光纤芯层并在其上溅射金纳米薄膜层，将制备好的传感器浸入不同折射率的液体中，使用光谱分析仪观察光谱的移动。实验结果表明:当塑料光纤SPR传感器测量折射率变化范围在1.333~1.406的液体时，可以通过光谱观察到随着液体折射率的增大，等离子体共振吸收峰位置也不断地向波长增大的方向移动，并且二者之间存在线性关系，其灵敏度为7.5×10-4 RIU/nm。该传感器探头具有灵敏度高、小型化、易制备、低成本的特点。     

内置调制层型光纤表面等离子体波共振传感器研究

研究了一种基于内置调制层结构的光纤表面等离子体波共振(SPR)传感器。通过在金膜与纤芯的内侧增覆具有不同厚度和属性的光学透明薄膜作为内调制层,构成了性能独特的光电复合薄膜,起到调节倏逝波矢量和金膜表面等离子体振荡波矢量的双重作用,进而控制共振效应,为调节灵敏度提供依据。采用时域有限差分方法对内置调制层结构光纤SPR共振激励模型属性进行数值仿真。在此基础上,研制了用于液体折射率测量的内置调制层型光纤SPR传感探针。实验结果表明,该传感器在1.335～1.392折射率范围内,随着待测液体折射率的增大,SPR共振光谱向长波方向偏移,且灵敏度达到2263.1nm/RIU,与基于纤芯-金膜-环境介质三层结构的常规光纤SPR传感器相比提高一倍,能够更好地满足环境折射率检测的需求。     

基于全相位滤波技术的光纤表面等离子体共振传感解调算法

基于生物样品检测对折射率传感的迫切需求,构建一种全光纤表面等离子体共振(surface plasmon resonance,SPR)系统,并针对其设计了基于全相位滤波技术的SPR特征波长传感解调算法.基于系统仿真,理论计算了光纤SPR传感器的折射率传感灵敏度.采用全相位滤波技术提取光纤SPR传感器透射光谱的特征波长,理论推导了全相位滤波器的解析表达式.实验结果表明,使用本算法的光纤SPR传感器折射率传感灵敏度为1640.4 nm/RIU,折射率检测的分辨率是7.36×10~(-4)RIU,与传统方法相比,有效提高了系统的检测精度和抗光源扰动性能,降低了实验成本.     

反射式光纤表面等离子体波共振传感器特性研究

研究了一种基于表面等离子体波共振(SPR)光谱分析的折射率检测新方法。研究发现,表面等离子体波共振效应光谱特征的折射率灵敏度会随着液体性质变化而发生改变。根据折射率测量范围不同,分别选择共振波长和共振强度作为检测参量,实现理论折射率分辨力达到10~(-5)数量级以上。在理论分析和实验基础上,设计出一种基于共振光强检测的终端反射式光纤表面等离子体波共振效应传感系统,采用将传感信号和基准光信号的比值作为液体折射率变化的度量值。在1．3325～1．3991的折射率测量范围内,度量值与折射率之间呈现单调递减关系,线性相关系数为0．9983。通过定义耦合系数,还可实现对表面等离子体波共振效应效应强弱和变化趋势的评估。     

基于表面等离子体共振和定向耦合的D形光子晶体光纤折射率和温度传感器

利用光子晶体光纤结构的灵活性和性能的优越性, 设计了一种基于D形光子晶体光纤的折射率和温度传感器. 在D形光子晶体光纤表面抛磨并镀上金纳米薄膜, 作为表面等离子体共振传感通道用来测量液体折射率; 在包层的一个空气孔中填充温敏液体甲苯, 作为定向耦合通道实现对温度的测量. 进一步的数值计算发现, 基于定向耦合效应的温度传感和基于表面等离子体共振的折射率传感相互独立, D形光子晶体光纤同时进行折射率和温度传感检测. 在各向异性的完美匹配层边界条件下利用全矢量有限元法对该传感器特性进行了数值研究, 发现D形光子晶体光纤的空气孔直径决定了定向耦合吸收峰的中心波长和温度传感的灵敏度, 金薄膜的厚度和D形结构的抛磨深度仅影响表面等离子体共振峰的相对强度. 结果表明: 该传感器在-10–80 ℃的温度范围内具有11.6 nm/℃的温度灵敏度, 在1.34–1.44折射率范围内折射率灵敏度最高可达26000 nm/RIU.     

螺旋形塑料光纤表面等离子体共振折射率传感器

研究了基于波长调制的螺旋形塑料光纤(plastic optical fiber, POF)表面等离子体共振(surface plasmon resonance, SPR)折射率传感器。采用机械热压和扭曲法将塑料光纤制备成螺旋形,在螺旋形POF上通过磁控溅射蒸镀一定厚度(约50 nm)的金属薄膜来激励SPR效应,从而形成螺旋形POF-SPR传感器。通过对螺旋形POF-SPR传感器的结构进行修饰,研究不同结构参数对折射率传感特性的影响。实验结果表明:由厚度为500μm扁平形POF扭制、螺纹数为4的螺旋形POF-SPR传感器具有较好的线性度和折射率传感特性,在折射率为1.335～1.400范围内测得的灵敏度为1 262 nm/RIU。该传感器具有成本较低、制备简单、结构稳定等优点。     

Numerical study of a highly sensitive surface plasmon resonance sensor based on circular-lattice holey fiber

A new design of surface plasmon resonance (SPR) sensor employing circular-lattice holey fiber to achieve high-sensitivity detection is proposed. The sensing performance of the proposed sensor is numerically investigated and the results indicate that our proposed SPR sensor can be applied to the near-mid infrared detection. Moreover, the maximum wavelength sensitivity of our proposed sensor can reach as high as 1.76×10⁴ nm/refractive index unit (RIU) and the maximum wavelength interrogation resolution can be up to 5.68×10^-6 RIU when the refractive index (RI) of analyte lies in (1.31, 1.36). Thanks to its excellent sensing performance, our proposed SPR sensor will have great potential applications for biological analytes detection, food safety control, bio-molecules detection and so on.     

Cross-point analysis for a multimode fiber sensor based on surface plasmon resonance

A novel analysis based on surface plasmon resonance (SPR) with a side-polished multimode fiber and a white-light (halogen light) source is presented. The sensing system is a multimode optical fiber in which half of the core has been polished away and a 40 nm gold layer is deposited on to the polished surface by dc sputter. The SPR dip in the optical spectrum is investigated with an optical spectrum analyzer (OSA). In our SPR fiber sensor, the use of liquids with different refractive indices leads to a shift in the spectral dip in the SPR curve. The cross point (CP) of the two SPR spectra obtained from the refractive-index liquid and the deionized water measurements was observed with the OSA. The CP is shifted sensitively in wavelength from 630 to 1300 nm relative to a change in the refractive index of the liquid from 1.34 to 1.46. High sensitivities of 1.9 x 10(-6) refractive-index units (RIUs) in the range of the refractive index of the liquid from 1.40 to 1.44 of 5.7 x 10(-7) RIUs above the value of 1.44 are proposed and demonstrated in our novel SPR analysis.     

基于D型双芯PCF的近红外宽检测范围SPR折射率传感器

现有报道的PCF-SPR折射率传感器的检测范围普遍较窄,不能实现低折射率的检测,且工作波段多数集中在可见光或通信波段,这限制了传感器的应用范围.鉴于此,提出了一种基于D型双芯PCF结构的SPR传感器,使用氧化铟锡作为等离子体材料沉积在D型PCF抛光表面,并对该传感器的理论模型进行了分析,包括金属参数对传感性能的影响,P...     

Microstructured fiber based plasmonic index sensor with optimized accuracy and calibration relation in large dynamic range

A novel surface plasmon resonance photonic sensor is proposed using an index-guided microstructured fiber with an analyte channel introduced into the central core. Compared with the previous designs of porous fiber core, variation of the signal amplitude with exterior refractive index is demonstrated to be contrary to that of the sensitivity in the proposed fiber, contributing to optimized detecting accuracy over a large refractive index range of 1.33 to 1.42. By carefully choosing the central channel size, the analyte-filled core can achieve narrower resonance spectral width and higher signal to noise ratio (SNR) than the air-filled core. Sensor responses are also studied in this paper based on two spectral interrogation methods, including monitoring single resonance shift and measuring change in the resonance separation. For both methods, response linearity has been improved considerably through partially filling the core with analyte. The maximal sensitivity reaches 10^− 6 refractive index unit (RIU). The linear sensing performance along with the broad measurement range is very promising in the application of the proposed sensor as sensitive refractometer.     

Liquid refractive index sensor with three-cascaded microchannels in single-mode fiber fabricated by femtosecond laser-induced water breakdown

Liquid refractive index sensor with three-cascaded microchannels in single-mode fiber was fabricated by femtosecond laser-induced water breakdown. When the liquid is filled in three microchannels across the fiber core, the transmission spectrum of the sensor shows interference peaks. The refractive index of liquid can be sensed accurately based on both the wavelength shift and loss change of interference peaks. The refractive index sensitivities of wavelength shift and loss change reach to as high as ?2,406.1 nm/RIU and ?156.8 dB/RIU, respectively. The sensor is insensitive to the refractive index change of liquid caused by environmental temperature. It can be used for liquid refractive index sensing with high sensitivity, especially for water pollution monitoring.     

Simultaneous measurement of refractive index and temperature using dual-period grapefruit microstructured fiber grating

By cascading the long period fiber grating (LPFG) and fiber Bragg grating (FBG) in grapefruit microstructured fiber, a novel dual-period fiber grating sensor is proposed. The refractive index and temperature are measured simultaneously by using the different sensitivity of FBG and LPFG. The relationship between dual-period fiber grating transmission spectrum and refractive index, resonant wavelengths and temperature are analyzed theoretically, respectively. The simulation results show that the accuracy of the sensor in measuring refractive index and temperature is estimated to be 2319.6 nm/RIU in a range from 1.33 to 1.36 and 0.017 nm/°C from 0 °C to 100 °C, respectively. Thus, the sensor has high refractive index sensitivity, and can provide the theoretical foundation for the optical fiber biosensor.     

基于空气孔微结构光纤的表面等离子体共振折射率传感器北大核心CSCD

提出了一种基于表面等离子体共振(SPR)效应增强的光子晶体光纤折射率传感器。该传感器结构通过光纤熔接机拼接光子晶体光纤(PCF),在光子晶体光纤中间引入一个空气孔形成PCF-空气孔-PCF的光纤传感结构,随后使用磁控溅射镀膜工艺在其表面沉积一层薄金膜制备而成。实验探究了折射率及温度对传感器的响应。结果表明,在1.333~1.389的折射率范围内,所提出的传感器的平均折射率灵敏度为2 142.52 nm,且测量线性度为0.981,品质因子约13.10。实验结果表明该传感器对温度不敏感。相比于无空气孔的PCF传感结构,引入的空气孔增强了SPR效应,使得传感器拥有良好的共振峰深度。得益于上述优势,该类型传感器有望在生物医学、环境监测等领域得到应用。     

基于光纤气泡和纤芯失配的Mach-Zehnder干涉液体折射率传感器

介绍了一种基于光纤气泡和纤芯失配的Mach-Zehnder干涉液体折射率传感器. 将两根纤芯经过腐蚀的普通单模光纤熔接在一起, 在熔接点处形成一个气泡, 在距气泡20 mm处级联一段20 mm的细芯光纤, 再接入一段单模光纤, 形成单模光纤-气泡-单模光纤-细芯光纤-单模光纤结构的传感器. 气泡与光纤芯径失配处的两个节点起到光纤耦合器的作用, 从而形成光纤Mach-Zehnder干涉仪. 环境液体折射率的变化,将使得传感器透射谱能量发生变化, 通过测量干涉谱波峰峰值能量从而实现对折射率的测量. 并对所制作传感器的折射率响应特性进行了实验研究, 实验结果表明干涉谱波峰峰值能量与环境液体折射率之间存在良好的线性关系, 当环境液体折射率变化范围在1.351–1.402时, 响应灵敏度为143.537 dB/RIU, 线性度0.996. 该传感器在生物化学领域有较好的应用前景. 关键词： 光纤气泡 纤芯失配 Mach-Zehnder干涉仪 折射率传感     

Sensitivity enhancement for a multimode fiber sensor with an axisymmetric metal grating layer

This paper proposes a novel design for a surface plasmon resonance (SPR) fiber sensor with an axisymmetric sub-wavelength metal grating layer. The relationship between the sensor performance (the sensitivity S and the quality factor Q of the SPR dip) and the characteristic parameters are investigated. Numerical simulation results show that the proposed sensor can achieve a maximum sensitivity of 13,000 nm/RIU (refractive index unit) for a refractive index range from 1.3 to 1.4.     

Design of fiber Bragg grating-based Fabry–Perot sensor for simultaneous measurement of humidity and temperature

A new sensor for simultaneous measurement of humidity and temperature is proposed. The sensor consists of Fabry–Perot cavity formed by two identical uniform fiber Bragg gratings. To make the cavity serves as humidity sensor, moisture sensitive polymer, which is polyimide, is coated on the FBG and on the cavity with different thickness. When the sensor is exposed to the relative humidity change, the polyimide will expand and stretch the fiber and induces strain on the FBG and on the cavity. The induced strain alters the grating period, cavity length and effective refractive index of fiber. The simulation results show that the humidity sensitivity and thermal sensitivity are 1.92 pm/%RH and 8.87 pm/°C, respectively, for polyimide coating thickness of 10 μm on the FBG and 15 μm on the cavity.     

基于激光微加工的新型光纤法布里-珀罗折射率传感器

提出了一种新型的光纤法布里-珀罗(F-P)折射率传感器,该传感器由单模光纤头端面和靠近该端面的由157 nm激光加工而成的短空气腔构成.短空气腔两个端面的反射光和光纤头端面的反射光发生干涉形成了传感器的反射谱干涉条纹.干涉条纹的对比度受光纤头端面外部的折射率影响,在干涉条纹包络的波谷处具有最大的对比度,外部待测折射率可通过计算该处的对比度得到.传感器对温度不敏感同,测量范围广.在1.33至1.441范围内,折射率灵敏度约为27 dB,分辨率约为1.12X10-4;在1.45～1.62范围内.折射率灵敏度约为24 dB,分辨率约为1.26×10-4.     

Fiber-optic Fabry-Prot strain sensor based on graded-index multimode fiber

By using a graded-index multimode fiber (GI-MMF) with a relatively flat index profile and high refractive index of the fiber core, a microextrinsic fiber-optic Fabry Prot interferometric (MEFPI) strain sensor is fabricated through chemical etching and fusion splicing. Higher reflectance of the microcavity is obtained due to the less-curved inner wall in the center of the fiber core after etching and higher index contrast between the GI-MMF core and air. The maximum reflection of the sensor is enhanced 12 dB than that obtained by etching of the Er- or B-doped fibers. High fringe contrast of 22 dB is obtained. The strain and temperature responses of the MEFPI sensors are investigated in this experiment. Good linearity and high sensitivity are achieved, with wavelength-strain and wavelength-temperature sensitivities of 7.82 pm/με and 5.01 pm/°C, respectively.