Highly sensitive miniature photonic crystal fiber refractive index sensor based on mode field excitation

A highly sensitive miniature photonic crystal fiber refractive index sensor based on field mode excitation is presented. The sensor is fabricated by melting one end of a photonic crystal fiber into a rounded tip and splicing and collapsing the other end with a single-mode fiber. The rounded tip is able to induce cladding mode excitation, which resulted in an additional phase delay. Linear response of 262.28 nm/refractive index unit in the refractive index range of 1.337 to 1.395 is obtained for the physical length of a 953 μm sensor. The sensor is also shown to be insensitive to environmental temperature.     

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.     

Refractive index sensor based on high-order surface plasmon resonance in gold nanofilm coated photonic crystal fiber

We propose a novel kind of wide-range refractive index optical sensor based on photonic crystal fiber(PCF) covered with nano-ring gold film.The refractive index sensing performance of the PCF sensor is analyzed and simulated by the finite element method(FEM).The refractive index liquid is infiltrated into the cladding air hole of the PCF.By comparing the sensing performance of two kinds of photonic crystal fiber structures, a wide range and high sensitivity structure is optimized.The surface plasmon resonance(SPR) excitation material is chose as gold, and large gold nanorings are embedded around the first cladding air hole of the PCF.The higher order surface plasmon modes are generated in this designed optical fiber structure.The resonance coupling between the fundamental mode and the 5 th order surface plasmon polariton(SPP)modes is excited when the phase matching condition is matched.Therefore, the 3 rd loss peaks appear obvious red-shift with the increase of the analyte refractive index, which shows a remarkable polynomial fitting law.The fitnesses of two structures are 0.99 and 0.98, respectively.When the range of refractive indices is from 1.40 to 1.43, the two kinds of sensors have high linear sensitivities of 1604 nm/RIU and 3978 nm/RIU, respectively.     

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.     

Highly sensitive photonic crystal fiber biosensor based on titanium nitride

A highly sensitive surface plasmon resonance photonic crystal fiber (PCF) biosensor based on Titanium Nitride (TiN) as a new alternative plasmonic material is proposed and analyzed. The TiN has high stability, high conductivity, and corrosion resistance which make it an ideal material for nanofabrication. The suggested biosensor is analyzed by full vectorial finite element method with perfectly matched layer as boundary conditions. In this paper, the biosensor geometrical parameters are studied to achieve high sensitivity for both polarized modes. A refractive index sensitivity of 7700 and 3600 nm/RIU for quasi-transverse electric and quasi transverse magnetic modes, respectively, are obtained. Additionally, the reported biosensor could be used for detecting an unknown analyte refractive index ranging from 1.32 to 1.34 with a high linearity. Further, the proposed biosensor structure is easy for fabrication using standard PCF fabrication current technologies.     

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。     

Enhanced sensitivity of hemoglobin sensor using dual-core photonic crystal fiber

A Hemoglobin (Hb) biosensor based on dual-core photonic crystal fiber is proposed and analyzed. In this paper, the effective refractive index dependency on the Hb concentration within a blood sample is utilized in obtaining the transmission spectrum variation. The results are calculated using full vectorial finite element method. Through this study, the effect of the structure geometrical parameters on the sensor performance is optimized to maximize the sensor sensitivity. The numerical results show a sensitivity of 8.013 nm/g/dL for the X-polarized mode at 3.7 cm fiber length and 7.68 nm/g/dL for the Y-polarized mode at 3.2 cm fiber length of the proposed sensor.     

基于包层模的光纤布拉格光栅折射率传感特性

提出了基于光纤布拉格光栅(FBG)包层模式的折射率传感方案。实验中,利用不同浓度的丙三醇水溶液作为外界折射率传感溶液,采用氢氟酸溶液化学腐蚀的方法来减小光纤包层的直径以增大包层模式对外界折射率的敏感度,研究了腐蚀后光纤布拉格光栅包层模式的耦合波长对外部折射率的变化关系。实验结果表明在1.3300~1.4584的折射率范围内,包层模式耦合波长随外界折射率增大而增大,在接近光纤包层折射率处具有很高的折射率灵敏度,最大达到了172 nm/riu(refractive index unit)。而且,包层模谐振的光谱半峰全宽(约0.07 nm)仅为布拉格纤芯模谐振光谱半峰全宽的1/4,能够获得更好的传感精度。     

应用于液压传感的光子晶体光纤特性

为实现结构紧凑、高灵敏度的光纤压力(液压)传感器,提出了一种应用于液压传感的边孔结构光子晶体光纤.基于全矢量有限元方法,研究了传统光子晶体光纤和边孔结构光子晶体光纤的有效折射、模式等特性以及在液压情况下的应力和应力特性.根据光弹效应给出了传统光子晶体光纤和边孔结构光子晶体光纤在液压情况下的折射率变化特性.模拟结果表明边孔结构光子晶体光纤可以获得更大的液压传感灵敏度,增大边孔半径可以提高液压传感灵敏度,因此结构优化的边孔结构光子晶体光纤可以实现高灵敏度的光纤压力(液压)压力传感器.     

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.     

应用于液压传感的光子晶体光纤特性

为实现结构紧凑、高灵敏度的光纤压力(液压)传感器,提出了一种应用于液压传感的边孔结构光子晶体光纤.基于全矢量有限元方法,研究了传统光子晶体光纤和边孔结构光子晶体光纤的有效折射、模式等特性以及在液压情况下的应力和应力特性.根据光弹效应给出了传统光子晶体光纤和边孔结构光子晶体光纤在液压情况下的折射率变化特性.模拟结果表明边孔结构光子晶体光纤可以获得更大的液压传感灵敏度,增大边孔半径可以提高液压传感灵敏度,因此结构优化的边孔结构光子晶体光纤可以实现高灵敏度的光纤压力(液压)压力传感器.     

基于游标效应的双芯光子晶体光纤温度传感器

设计了一种基于双芯光纤耦合效应和游标效应的高灵敏度温度传感器,传感器是由2个相差一定长度的双芯光子晶体光纤和单模光纤级联构成。双芯光子晶体光纤通过级联实现游标效应,同时对纤芯中间的气孔填充乙醇实现温度传感。仿真结果表明,该温度传感器在35 ℃～45 ℃范围内的平均温度灵敏度可达?20.37 nm/℃。与单纯依靠双芯光子晶体光纤能量耦合效应的传感器相比,该传感器的温度检测灵敏度提高了10倍。     

折射率不敏感的级联型单模-少模-单模光纤温度传感器

提出了一种折射率不敏感的级联型单模-少模-单模光纤温度传感器。在制作传感器的过程中,设置熔接电流为100 mA,通过将少模光纤与单模光纤进行无错位熔接,以激发稳定的传输模式,形成光纤马赫-曾德尔干涉仪。由于外界环境的改变会引起少模光纤中不同模式之间相位差的改变,从而导致干涉条纹的漂移,因此通过检测干涉条纹的漂移量就可以实现待测参数的检测。少模光纤可以传输LP₀₁,LP₁₁,LP₂₁,LP₀₂共四种模式的光。实验中对长度为81.5 mm的传感器光谱进行分析可知,发生干涉的两个模式主要是LP₀₁模和LP₁₁模。利用该长度的级联型单模-少模-单模光纤传感器进行折射率和温度传感实验,结果表明,随着传感器温度不断的增加,其传输光谱出现了明显的蓝移现象,在27.6~93.8 ℃的温度变化范围内,灵敏度高达-85.9 pm·℃-1,且具有较好的线性度;在甘油折射率为1.347 1~1.443 9变化范围内,其传输光谱没有出现明显的漂移现象,灵敏度仅为3.697 34 nm·RIU-1,具有折射率不敏感特性。因此,相对于传统的包层模干涉型与多模干涉型光纤传感器,所提出的基于FMF的传感器更易于实现对传输模式的控制与分析,且具有结构简单、易于制备、灵敏度高等优点,能够避免温度与折射率同测的交叉敏感问题,可用于电力系统、生物医学、航空航天等领域的温度检测。     

Photonic crystal fiber tip interferometer for refractive index sensing

In this paper we present an interferometer based on photonic crystal fiber (PCF) tip ended with a solid silica-sphere for refractive index sensing. The sensor is fabricated by splicing one end of the holey PCF to a single mode fiber (SMF) and applying arc at the other end to form a solid sphere. The sensor has been experimentally tested for refractive index and temperature sensing by monitoring its wavelength shift. Measurement results show that the sensor has the resolution of the order of 8.7×10(-4) over the refractive index range of 1.33-1.40, and temperature sensitivity of the order of 10 pm/°C in the range of 20-100 °C.     

High sensitivity dual core photonic crystal fiber sensor for simultaneous detection of two samples

The optical control ability of photonic crystal fiber (PCF) is a distinctive property suitable for improving sensing and plasma performance. This article proposes a dual-core D-channel PCF sensor that can detect two samples simultaneously, which effectively solves the problems of coating difficulty and low wavelength sensitivity. The PCF has four layers of air holes, which dramatically reduces the optical fiber loss and is more conducive to the application of sensors in actual production. In addition, by introducing dual cores on the upper and lower sides of the central air hole, reducing the spacing between the core and the gold nanolayer, a stronger evanescent field can be generated in the cladding air hole. The optical fiber sensor can detect the refractive index of two samples simultaneously with a maximum sensitivity of 21300 nm/RIU. To the best of our knowledge, the sensitivity achieved in this work is the highest sensitivity with the dual sample synchronous detection sensors. The detection range of the refraction index is 1.35-1.41, and the resolution of the sensor is 4.695×10^-6. Overall, the sensor will be suitable for medical detection, organic chemical sensing, analyte detection, and other fields.     

基于无芯光纤的多参数测量传感器

设计并制作了一种基于单模-无芯-单模-无芯-单模光纤结构的马赫-曾德尔传感器,可用来同时测量折射率和温度.该传感器中,两处无芯光纤充当输入、输出耦合器,中间单模光纤作为传感臂.利用有限元仿真和理论分析,确定耦合器和传感臂的最优长度为15 mm.在无芯光纤中激发出的高阶模进入单模光纤的包层传输,由于倏逝场的作用,受到环境折射率和温度的影响.选取透射谱不同干涉级次的波谷作为研究对象,实现了折射率和温度的同步测量.实验结果表明:1545 nm附近干涉谷的折射率和温度灵敏度分别为–153.89 nm/RIU(refractive index unit)和0.166 nm/℃;1570 nm附近干涉谷的折射率和温度灵敏度分别为–202.74 nm/RIU和0.183 nm/℃.该传感器在实现折射率和温度同步测量的同时,仍能保持较高灵敏度,在生物医疗等方面有着较好的应用前景.     

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.     

Long period grating cascaded to photonic crystal fiber modal interferometer for simultaneous measurement of temperature and refractive index

We propose and demonstrate a novel and simple dual-parameter measurement scheme based on a cascaded optical fiber device of long-period grating (LPG) and photonic crystal fiber (PCF) modal interferometer. The temperature and refractive index (RI) can be measured simultaneously by monitoring the spectral characteristics of the device. The implemented sensor shows distinctive spectral sensitivities of -30.82 nm/RIU (refractive index unit) and 47.4 pm/°C by the LPG, and 171.96 nm/RIU and 10.4 pm/°C by the PCF modal interferometer. The simultaneous measurement of the temperature and external RI is experimentally demonstrated by the sensor. The temperature shift and RI shift calculated by the sensor matrix agree well with the actual temperature and RI change in the experiment.     

Fiber in-line Mach-Zehnder interferometer constructed by selective infiltration of two air holes in photonic crystal fiber

A fiber in-line Mach-Zehnder interferometer is fabricated through selective infiltrating of two adjacent air holes of the innermost layer in the solid core photonic crystal fiber, assisted by femtosecond laser micromachining. The liquid infiltrated has higher refractive index than that of the background silica, and, hence, the two rods created can support a guide mode with lower effective refractive index than that of silica. The interference is produced by the fiber fundamental mode and the guide mode. The free spectral range (FSR) of the interferometer is found to be dependent on the photonic crystal fiber length, and a large FSR corresponds to a short photonic crystal fiber length. Such an interferometer device is robust and exhibits extremely high temperature sensitivity (～7.3?nm/°C for the photonic crystal fiber length of 3.4?cm) and flexible operation capability.     

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.