基于侧边抛磨光纤表面等离子体共振的折射率和温度传感研究

用轮式侧边抛磨法制作侧边抛磨光纤,通过磁控溅射法溅射金膜制成侧边抛磨光纤表面等离子体共振(SPR)传感器,并通过理论和实验对传感器的折射率灵敏度以及温度特性做了深入研究。结果表明表面等离子体共振波长随待测样品折射率的增大向长波长方向漂移,平均折射率灵敏度为4.1×103 nm/RIU(RIU为单位折射率),高于已报道的结果;共振波长随待测样品温度的升高向短波长方向漂移,平均温度灵敏度为0.36nm/℃,故该光纤SPR传感器具有更强抗温度漂移能力和更高的高折射率灵敏度,其在生物化学传感领域有重要的应用。     

TiO2纳米粒子增强的光纤损失模式共振折射率传感器

以多模光纤为基底来实现损失模式共振(LMR)折射率传感的灵敏度较低，在利用铟锡氧化物(ITO;In₂O₃和SnO₂的质量分数分别为90%和10%)激发光纤LMR传感的基础上，在ITO薄膜上静电组装二氧化钛(TiO₂)纳米粒子，实现折射率灵敏度的提升。使用Kretschman结构模型对传感器进行理论分析，仿真分析了LMR共振阶数与ITO薄膜厚度的关系，以及ITO作为LMR膜层实现折射率传感的可行性。通过在光纤侧壁磁控溅射ITO薄膜以产生LMR效应，制备ITO-LMR折射率传感器。通过折射率传感实验对ITO-LMR和TiO₂-ITO-LMR两种传感器进行性能测试，在1.3333～1.3840的折射率变化范围内，TiO₂-ITO-LMR传感器灵敏度可达1651.659 nm/RIU，相较于ITO-LMR折射率传感器，其灵敏度提升了3.058倍。     

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.     

波长调制型表面等离子体共振的传感特性研究

表面等离子体共振(SPR)光学传感器能实现生物医学的快速、 无标记、 高精度检测,是生物化学分析的重要方法。 研制了基于波长调制型的Kretschmann结构表面等离子体共振(SPR)生物传感系统,研究了在体溶液传感方式下的传感性能。 利用不同浓度的乙醇和乙二醇溶液进行体溶液传感测试。 实验结果表明,在折射率低时共振波长对折射率变化响应的灵敏度低,但响应的线性度高;随着折射率增大,共振波长对折射率的响应变化的灵敏度提高。 在1.407 0～1.430 RIU折射率范围内,灵敏度高达11 487 nm·RIU-1。 传感器的共振波长的稳定性为0.213 8 nm,可分辨最小折射率趋近10-6 RIU。 所研制的波长调制型表面等离子共振传感器操作简单、 灵敏度高、 检测范围大,可实现浓度极低生物标记物的有效检测,在化学、 生物传感领域有重要的应用。     

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。     

复合金属光栅模式分离与高性能气体传感器应用

为实现近红外波段表面等离子体共振(SPR)模式的分裂和移动, 同时提高光栅基SPR传感器的品质因数, 提出了一种由双金属光栅构成的新型复合结构光栅, 并研究了其气体传感特性. 运用有限时域差分算法对该结构进行了数值模拟, 发现由复合金属光栅激发的SPR出现模式分裂的现象. 通过增大双金属光栅阵列间的相对位移改变原结构的对称性, 导致复合金属光栅分裂的SPR模式朝相反方向移动. 当相对位移量进一步增大到双光栅合并成新的单一光栅时, 随光栅结构对称性的恢复, 分裂的两共振模式最后又重新合并为一个模式. 如果待测物的折射率为1.01≤n_a≤1.05, 当相对位移量为0时, 基于复合光栅结构气体传感器的折射率灵敏度为1207.5 nm/RIU, 且品质因数达到1290.7; 当相对位移量为100 nm时, 与双共振模式对应的折射率灵敏度分别为1205.0 nm/RIU和1210.0 nm/RIU, 品质因数分别为1295.4和762.3. 因此, 复合光栅SPR传感器具有超高品质因数的性能, 使得它在生物化学传感领域中有巨大的应用潜力.     

基于银/二氧化钛复合膜的表面等离子共振气体传感器

表面等离子体共振是一种免标记的传感技术,当介质周围的介电常数发生改变时,则SPR谐振光谱特性也会随之改变。因此表面等离子体共振传感技术已广泛应用于生物化学和环境监测等领域。由于二氧化钛（TiO₂）覆盖层不仅可以保护金属层,还能调谐SPR谐振的光谱强度和谐振波长于近红外波段,应用于1550 nm的光纤传感,其氧化还原反应还能使其用于检测气体。由于氢气易燃易爆性,随着氢能源的广泛应用,因此对低浓度氢气检测技术研究具有特殊的意义。提出一种可更换银/二氧化钛复合膜的表面等离子共振的气体传感器,研究了SPR传感器在1 550 nm近红外波段对气体的敏感特性。研制了可更换银/二氧化钛复合膜的表面等离子共振（SPR）气体传感器。研究了在近红外波段对气体的表面等离子体共振光谱特性。仿真计算Kretschmann棱镜耦合的四层结构模型的共振光谱强度与银膜厚度,二氧化钛厚度和棱镜材料的关系,优化了Ag和TiO₂层的厚度以获得最大灵敏度,得到的最佳膜厚是45 nm Ag和110 nm TiO₂。Ag/TiO₂薄膜设计为可更换的一次性气敏膜,采用蒸镀和溅射方法镀膜,制备成本文所使用的 SPR传感器。利用Ag/TiO₂薄膜在复合界面产生SP共振光谱的移动,对气体进行测试。采用Kretschmann棱镜耦合结构的光谱波长检测实验系统。固定光源和入射角,测量波长的偏移量。宽光源（波长范围：1 462～1 662 nm）通过环形器、准直器,照射到棱镜和可更换的Ag/TiO₂敏感膜,经全反射(TIR)后,再由高反射镜反射回传感膜,并以相同的TIR角和光路再次反射回到准直器,从而被光谱仪检测。实验结果表明,Ag/TiO₂复合膜可以调谐共振波长到1 550 nm近红外波段,增强该传感器的光谱灵敏度,低浓度（14.7%～25%）氢气下的灵敏度可达-8.305 nm·%-1。并且可通过更换气敏膜检测不同的气体,增加生物相容性和气体传感能力。     

开放式多通道多芯少模光纤表面等离子体共振生物传感器

基于多芯少模光纤结构特性,提出了一种具有开放式感知通道的多芯少模光纤表面等离子体共振生物传感器.建立了多芯少模光纤表面等离子体共振生物传感器的模型,利用有限元方法分析了纤芯气孔间距、膜层厚度、膜层材料以及不同传输模式对传感器性能的影响,并讨论了传感器多通道感知性能.仿真分析发现,纤芯气孔间距决定了倏逝波的耦合强度,材料特性和模式共同影响了表面等离子体共振峰的位置和灵敏度.经过计算可知:当单个凹槽传感通道上沉积100 nm铟锡氧化物薄膜,分析物折射率范围为1.33—1.39时, LP11ax模式对应的平均光谱灵敏度为12048 nm/RIU(其中RIU为折射率单位,即refractive index unit),最高灵敏度为20824.66 nm/RIU,最大折射率分辨率可达4.8×10~(–6) RIU;当光纤外围凹槽镀上不同厚度的金膜、银膜和铟锡氧化物膜时,既可以单独探测生物物质,也可以联合检测同一生物物质,实现了传感通道的控制灵活性和测试物质的多样性.     

基于银/高纯铟复合膜的表面等离子体共振折射率传感器

为了解决单一金属膜结构的光纤表面等离子体共振（SPR）盐度传感器结构不稳定且灵敏度较低的问题,设计了一种高灵敏度的锥形三芯光纤结构的SPR盐度传感器。以银膜为激发表面等离子体共振的金属层,在其表面涂覆高纯铟以增强其稳定性。通过Kretschmann四层结构模型对传感器进行理论分析,结果表明,在光纤锥区纤芯模和包层模之间会出现强烈的模式耦合,在覆膜区会激发明显的等离子体共振。对涂覆银膜和高纯铟膜的SPR传感器进行折射率性能测试,在1.4%～3.6%的盐度变化范围内,涂覆银膜和高纯铟膜的SPR传感器灵敏度高达4989.34 nm/RIU,对应的盐度灵敏度为9.1 nm/%,比仅涂覆银膜的SPR传感器灵敏度提高了44%。     

单层膜体吸收与界面吸收研究

采用热透镜测量方法进行了SiO₂和HfO₂单层膜的体吸收与界面吸收分离研究.首先推导了光从薄膜侧及基底侧入射时单层膜内的驻波场分布,给出了单一厚度薄膜分离体吸收和界面吸收的计算方程式以及求解薄膜消光系数的方法.利用电子束蒸发工艺制备了半波长光学厚度(λ=1064 nm)的SiO₂和HfO₂单层膜,通过热透镜的测量数据实际分离了两种薄膜的体吸收和界面总吸收.计算结果表明,对于吸收小至10^{-6关键词： 驻波场理论 光热技术 薄膜吸收 消光系数}     

Bimetallic Silver–Gold Film Waveguide Surface Plasmon Resonance Sensor

Abstract

It is desirable that a surface plasmon resonance (SPR) sensor is highly sensitive to binding interactions within the sensing region, generate evanescent fields with long penetration depths, and utilize a metal film that is very stable even in extreme environmental conditions. In this study, we present the first example of a wavelength-modulated waveguide SPR sensor with a bimetallic silver–gold film for surface plasmon excitation. The underlying silver yields better evanescent field enhancement of the sensing surface, while the overlying gold ensures that the stability of the metallic film is not compromised. It is shown experimentally that in terms of dλ/dn, the bimetallic film waveguide SPR configuration has a sensitivity of 1232 nm/RIU, greater than two times improvement from the 594 nm/RIU achievable with single gold film waveguide SPR sensor. The higher sensitivity, compact nature, and better evanescent field enhancement of this configuration provides the potential to biosensing applications.     

Performances of different metals in optical fibre-based surface plasmon resonance sensor

The capability of various metals used in optical fibre-based surface plasmon resonance (SPR) sensing is studied theoretically. Four metals, gold (Au), silver (Ag), copper (Cu) and aluminium (Al) are considered for the present study. The performance of the optical fibre-based SPR sensor with four different metals is obtained numerically and compared in detail. The performance of optical fibre-based SPR sensor has been analysed in terms of sensitivity, signal-to-noise (SNR) ratio and quality parameter. It is found that the performance of optical fibre-based SPR sensor with Au metal is better than that of the other three metals. The sensitivity of the optical fibre-based SPR sensor with 50 nm thick and 10 mm long Au metal film of exposed sensing region is 2.373 μm/RIU with good linearity, SNR is 0.724 and quality parameter is 48.281 RIU^− 1. The thickness of the metal film and the length of the exposed sensing region of the optical fibre-based SPR sensor for each metal are also optimized.     

High-Sensitivity Sensor Based on Surface Plasmon Resonance Enhanced Lateral Optical Beam Displacements

We present a new optical sensor based on surface plasmon resonance （SPIt） enhanced lateral optical beam displacements. Compared with the traditional SPIt methods, the new method provides higher sensitivity to the sensor system. Theoretical simulations show that the refractive index （RI） detection sensitivity of the SPR sensor based on the displacement measurement has a strong dependence on the thickness of the metal film. When the optimal thickness of the metal film is selected, the RI resolutlon of the SPIt sensor is predicted to be 2.2 × 10^-7 refractive index units （RIU）. Furthermore, it is found that the incidence angle can be used as a parameter to adjust the operating range of the sensor to different refractive index ranges.     

Fiber-optic surface plasmon resonant sensor with low-index anti-oxidation coating

A multimode fiber-optic surface plasmon resonance(SPR) sensor with a MgF2 film as a modulated layer is studied.The fiber-optic SPR sensor is investigated theoretically,specifically the influence of the dielectric protecting layer,using a four-layer model.The sensor is then fabricated with the optimal parameters suggested by the theoretical simulation.The sensor has a high sensitivity in the analyte refractive index(RI) range of 1.33-1.40.The best sensitivity of 4 464 nm/RIU is achieved in the experiment.The use of dielectric film(MgF2) can not only modulate the resonance wavelength of the sensor,but also protect the silver film from oxidation.     

Ultracompact refractive index sensor based on microcavity in the sandwiched photonic crystal waveguide structure

A refractive index (RI) sensor based on the two-dimensional photonic crystal is presented. The sensor is formed by a point-defect resonant cavity in the sandwiched waveguide structure. The transmission spectrums of the sensor with different ambient refractive indices ranging from n = 1.0 to n = 1.6 are calculated. The calculation results show that a change in ambient RI of Δn = 0.001 is apparent, the sensitivity of the sensor (Δλ/Δn) is achieved with 330 nm/RIU (when lattice constant a = 440 nm), where RIU means the refractive index unit; and the transmission efficiency in the RI range of 1.0-1.6 can reach about 40% to 70%, that make the detection of spectrum easy and feasible. The properties of the sensor are analyzed and calculated using the plane-wave expansion (PWE) method and simulated using the finite-difference time-domain (FDTD) method.     

Surface plasmon optical sensor with enhanced sensitivity using top ZnO thin film

Surface plasmon resonance (SPR) is one of the most sensitive label-free detection methods and has been used in a wide range of chemical and biochemical sensing. Upon using a 200 nm top layer of dielectric film with a high value of the real part ε′ of the dielectric function, on top of an SPR sensor in the Kretschmann configuration, the sensitivity is improved. The refractive index effect of dielectric film on sensitivity is usually ignored. Dielectric films with different refractive indices were prepared by radio frequency magnetron (RF) sputtering and measured with spectroscopic ellipsometry (SE). The imaginary part ε′′ of the top nanolayer permittivity needs to be small enough in order to reduce the losses and get sharper dips. The stability of the sensor is also improved because the nanolayer is protecting the Ag film from interacting with the environment. The response curves of the Ag/ZnO chips were obtained by using SPR sensor. Theoretical analysis of the sensitivity of the SPR sensors with different ZnO film refractive indices is presented and studied. Both experimental and simulation results show that the Ag/ZnO films exhibit an enhanced SPR over the pure Ag film with a narrower full width at half maximum (FWHM). It shows that the top ZnO layer is effective in enhancing the surface plasmon resonance and thus its sensitivity.     

Surface plasmon resonance based fiber optic sensor utilizing indium oxide

A highly sensitive surface plasmon resonance (SPR) based fiber optic sensor with indium oxide (In₂O₃) layer coated on the core of the optical fiber is presented and theoretically analyzed. The sensitivity of the SPR based fiber optic sensor has been evaluated numerically. It is shown that the proposed SPR based fiber optic sensor with In₂O₃ layer possesses high sensitivity in the near infrared region of spectrum, which needs attention to many environmental and security applications and offers more accurate and highly reproducible measurements. In addition, the sensitivity of the SPR based fiber optic sensor decreases with the increase in the thickness of In₂O₃ layer. With sensitivity as high as 4600 nm/RIU, the 170 nm thick In₂O₃ layer based fiber optic SPR sensor demonstrates better performance.     

Bimetallic Silver-Gold Film Waveguide Surface Plasmon Resonance Sensor

It is desirable that a surface plasmon resonance (SPR) sensor is highly sensitive to binding interactions within the sensing region, generate evanescent fields with long penetration depths, and utilize a metal film that is very stable even in extreme environmental conditions. In this study, we present the first example of a wavelength-modulated waveguide SPR sensor with a bimetallic silver-gold film for surface plasmon excitation. The underlying silver yields better evanescent field enhancement of the sensing surface, while the overlying gold ensures that the stability of the metallic film is not compromised. It is shown experimentally that in terms of dλ/dn, the bimetallic film waveguide SPR configuration has a sensitivity of 1232 nm/RIU, greater than two times improvement from the 594 nm/RIU achievable with single gold film waveguide SPR sensor. The higher sensitivity, compact nature, and better evanescent field enhancement of this configuration provides the potential to biosensing applications.     

Sensitivity enhancement of graphene coated surface plasmon resonance biosensor

In this paper, a highly sensitive surface plasmon resonance biosensor is presented using angular interrogation. Due to low sensitivity of conventional biosensor, graphene/two-dimensional transition metal are used in surface plasmon resonance biosensor to improve the sensitivity. Here, we propose a seven layer model of biosensor which shows by incorporating silicon layer in addition of transition metal dichalcogenides MoS₂ and graphene, the sensitivity of the proposed SPR biosensor can be greatly enhanced than the conventional gold film SPR sensors. It is observed that the highest sensitivity can be obtained by optimizing the structure with 8 nm thickness of silicon layer, one layer of MoS₂ and one layer of graphene. The highest sensitivity of our proposed sensor is 210°/RIU.     

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.