基于方形谐振器的表面等离子体波导传感器

本文利用方形谐振器与两个金属/介质/金属型波导结构耦合设计了一个亚波长的表面等离子体波导传感器,并通过有限元分析研究了此结构的传输特性。研究表明,通过谐振器耦合能有效增强共振波长的表面等离子体波的透射能力,同时减小两侧波导结构与方形谐振器之间的金属势垒层宽度可提高透射率。传感器的共振波长与介质材料的折射率之间存在着线性关系,1阶共振模的灵敏度可达1100nm/RIU。这种传感器可实现器件的小型化,在生物、工业传感领域有着很大的潜力。     

拉盖尔-高斯幂指数相位涡旋光束传输特性

为实现光折射率传感器小结构、高灵敏度的要求,根据表面等离极化激元的透射特性,提出了一种单挡板金属-介质-金属（MIM）波导耦合类云朵腔结构。此结构引用“腔中腔”的理念,在近场耦合作用下,类云朵腔所形成的较宽的连续态与金属挡板所形成的较窄的离散态经过干涉相长相消,可以产生三重不同模式的法诺共振。结合耦合模理论,对三重法诺共振的产生机理进行分析,并运用有限元分析法对此结构进行模拟仿真,定量分析了不同结构参数对折射率传感特性以及优质因子的影响。结果表明,三种共振模式的灵敏度分别为600,800,1083 nm/RIU,优质因子分别为5.08×10⁴、3.56×10⁵和1.17×10³。     

含双挡板金属-电介质-金属波导耦合方形腔的独立调谐双重Fano共振特性

基于表面等离子激元在亚波长结构的传输特性,设计了一种含双挡板金属-电介质-金属波导耦合两个方形腔的结构.由F-P谐振腔产生的宽谱模式与两个方形谐振腔产生的两个窄谱模式发生干涉作用,形成了独立调谐的双重Fano共振,而且可以通过改变两个方形腔的大小及填充介质实现双重Fano共振的独立调谐.基于耦合模理论,定性分析了该结构产生双重Fano共振的机理.利用有限元仿真的方法,定量分析了结构参数对可独立调谐双重Fano共振和折射率传感特性的影响.结果表明,优化参数后该结构的灵敏度分别高达1020和1120 nm/RIU, FOM值分别高达3.59×10~5和1.17×10~6.该结构可为超快光开关、多功能高灵敏度传感器和慢光器件的光学集成提供有效的理论参考.     

金属-介质-金属多层结构可调谐Fabry-Perot共振及高灵敏折射率传感

顶层透光、底层不透光的金属-介质-金属多层结构可以产生窄带完美吸收共振,用于测量介质层待测液体的折射率变化.本文通过构建Fabry-Perot共振解析模型,准确复现了该结构的响应光谱,给出了其共振波长、品质因子、半高全宽和灵敏度的解析表达式,并分析了介质层厚度对光谱的谐振波长和线宽的调谐机制,明确了其物理机理.基于8阶Fabry-Perot共振的金属-介质-金属多层结构,用于折射率传感时的品质因子及优值分别达到2162.8和1648.1 RIU–1.针对极小的折射率扰动,通过在奇异点状态叠加Fabry-Perot共振的调谐机制,提出了通过测量奇异点波长处反射系数的增加量或散射矩阵本征值的分裂量,实现对待测液体折射率的可调谐式传感的方案. Fabry-Perot模型解析结果显示,当待测液体的折射率变化为10–4 RIU时,基于8阶FabryPerot共振的金属-介质-金属多层结构的前向反射系数增加量和本征值分裂量分别达到0.319和1.1279.     

基于乙醇密封共振腔金属-介质-金属波导的高性能温度和折射率两用传感器

为了提高现有的亚波长量级温度传感器和折射率传感器的各项工作性能,本文基于表面等离激元提出了一种拥有尖锐峰的高灵敏度、高集成度的环八边形表面等离子体共振传感器.理论分析了以乙醇作为热敏填充材料使温度和有效折射率建立线性转换关系的可行性,并利用多模耦合模式理论(MICMT)对该传感器的透射峰进行了拟合和理论分析,再利用有限元法(FEM)进行了仿真分析,理论结果和仿真结果高度匹配.然后对环八边形共振腔的各项参数进行了有限元数值模拟,计算得出该传感器的最佳参数设置.和以往结构设计对比,该两用传感器拥有工作波段范围广、半峰全宽窄、易于集成等诸多优点,作为传感器的温度灵敏度和折射率灵敏度分别高达0.9 nm/℃和2400 nm/RIU.该结构兼具一些传统腔体的优点,为以后基于表面等离激元设计的微纳光子温度传感和折射率传感两用器件提供了一种高性能的腔体选择.     

单挡板MDM波导耦合圆盘腔的Fano共振双模式特性研究

基于表面等离子亚波长结构的传输特性与光子局域特性,提出了一种单挡板金属-电介质-金属(MDM)波导耦合圆盘腔结构。由圆盘腔形成的两个孤立态与金属挡板形成的较宽的连续态干涉相消,形成两种不同模式的Fano共振。结合耦合模理论分析了该结构形成Fano共振的传输特性,用有限元分析法对结构进行模拟仿真,定量分析了结构参数对折射率传感特性的影响。结果表明:优化后的结构在两种模式下的优质因子分别为1.7×105和1.36×105,折射率灵敏度分别为710nm/RIU和1105nm/RIU,可为解决传感器在折射率测量时的交叉敏感问题提供理论参考。     

基于金属-电介质-金属波导结构的等离子体滤波器的数值研究

基于金属-电介质-金属波导结构, 提出了一种含双侧多支节型等离子波导滤波器, 采用有限元法研究了其透射特性. 在该结构的透射谱中观察到了基于电磁诱导透明效应的四个窄带透射峰, 并通过模场分布有效阐释了透射谱线中峰值、谷值的产生的物理机理. 数值研究同时表明当每个支节长度线性增加时, 透射峰中心波长也将线性增加. 这一结果可用于指导可调谐、多通道窄带滤波器的设计.     

表面等离子体环形共振器的滤波性质

利用时域有限差分法研究了基于金属-绝缘体-金属结构的环形波导共振器的滤波特性.研究结果表明,环形波导中存在多个共振模式.共振波长受环形波导的内径调制,随着环形波导内径的增加共振波长发生红移.共振带宽受耦合距离调制,随着耦合距离的增加带宽显著地减小.     

单挡板金属-电介质-金属波导耦合圆盘腔级联多Fano共振差动传感

基于表面等离子亚波长结构的传输特性与光子局域特性,提出了一种单挡板金属-电介质-金属(MDM)波导耦合圆盘级联结构。由圆盘级联形成的孤立态与金属挡板形成的较宽连续态干涉相长相消,形成了两种不同模式的Fano共振。结合耦合模理论,分析了该结构形成Fano共振的传输特性,采用有限元分析法对结构进行了模拟仿真,定量分析了结构参数对折射率传感特性影响。根据折射率变化的物理机制,分析了温度和湿度在实际测量过程中对测量结果的影响,并采用差动传感的方法有效解决了传感过程中的交叉敏感问题。     

侧耦合谐振腔的多重独立可调谐Fano共振传感特性

基于表面等离极化激元在亚波长结构的传输特性,提出了一种含单挡板的金属-介质-金属(MIM)波导耦合双T型谐振腔的结构。在近场耦合作用下,单挡板形成的较宽连续态与单T型腔形成的较窄离散态,经过复杂的干涉相消形成非对称的双重Fano共振峰。基于耦合模理论,研究了单挡板MIM波导耦合单T型腔Fano共振的产生机理,并采用有限元分析法对该结构进行了模拟仿真。在此基础上,研究了含双T型腔结构的四重Fano共振形成过程,分析了上下T型腔结构参数对Fano共振峰的影响。结果表明,上下T型腔产生的Fano共振峰互不影响,且由单个T型腔可以实现两个Fano共振峰独立可调谐,故含金属挡板的MIM波导耦合双T型腔结构可以实现四个Fano共振峰独立可调谐。该结构可为差动传感器和波分复用器的设计提供有效的理论参考。     

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。     

A novel plasmonic refractive index sensor based on gold/silicon complementary grating structure

A novel complementary grating structure is proposed for plasmonic refractive index sensing due to its strong resonance at near-infrared wavelength.The reflection spectra and the electric field distributions are obtained via the finite-difference time-domain method.Numerical simulation results show that multiple surface plasmon resonance modes can be excited in this novel structure.Subsequently,one of the resonance modes shows appreciable potential in refractive index sensing due to its wide range of action with the environment of the analyte.After optimizing the grating geometric variables of the structure,the designed structure shows the stable sensing performance with a high refractive index sensitivity of 1642 nm per refractive index unit(nm/RIU)and the figure of merit of 409 RIU^-1.The promising simulation results indicate that such a sensor has a broad application prospect in biochemistry.     

Tunable plasmonic filter with circular metal–insulator– metal ring resonator containing double narrow gaps

Tunable filter based on two metal–insulator–metal (MIM) waveguides coupled to each other by a ring resonator with double narrow gaps is designed and numerically investigated by finite-difference time-domain (FDTD) simulations. The propagating modes of surface plasmon polaritons (SPPs) are studied. By introducing narrow gaps in ring resonators, the transmission in different resonance modes can be effectively adjusted by changing the gap width (g), and the transmitted peak wavelength has a nonlinear relationship with g. Another structure consisting two cascading ring resonators and regular MIM waveguide have also been proposed. The mechanism based on circular ring resonators with narrow gaps may provide a novel method for designing all-optical integrated components in optical communication and computing.     

Independently tunable dual resonant dip refractive index sensor based on metal—insulator—metal waveguide with Q-shaped resonant cavity

A plasmonic resonator system consisting of a metal—insulator—metal waveguide and a Q-shaped resonant cavity is proposed in this paper. The transmission properties of surface plasmon polaritons in this structure are investigated by using the finite difference in time domain (FDTD) method, and the simulation results contain two resonant dips. The physical mechanism is studied by the multimode interference coupled mode theory (MICMT), and the theoretical results are in highly consistent with the simulation results. Furthermore, the parameters of the Q-shaped cavity can be controlled to adjust the two dips, respectively. The refractive index sensor proposed in this paper, with a sensitivity of 1578 nm/RIU and figure of merit (FOM) of 175, performs better than most of the similar structures. Therefore, the results of the study are instructive for the design and application of high sensitivity nanoscale refractive index sensors.     

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.     

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。     

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.     

Hybrid photonic surface-plasmon-polariton ring resonators for sensing applications

We introduce a hybrid photonic surface plasmon ring resonator which consists of a silicon nitride (Si₃N₄) dielectric traveling-wave ring resonator vertically coupled to a thin layer of metallic strip ring resonator made of Silver (Ag) on top. The cladding is assumed to be porous alumina on top of the metal layer, which provides more surface area for the adsorption of target molecules and their efficient interaction with the surface plasmon wave excited at the metal-cladding interface. Simulations show that this hybrid structure has a large refractive index sensitivity due to the excitation of surface plasmon waves and also a relatively narrow resonance linewidth due to the large quality factor of the photonic ring resonator. The Finite Element method is used to systematically design the hybrid structure and to investigate the performance of the hybrid resonator as a refractive index sensor. The proposed structure is very compact and can be implemented on a chip in an integrated platform. Thus, it can be used for lab-on-a-chip sensing applications and is capable of being spectrally and spatially multiplexed for muti-analyte sensing.     

Slot-waveguide biochemical sensor

We report an experimental demonstration of an integrated biochemical sensor based on a slot-waveguide microring resonator. The microresonator is fabricated on a Si3N4-SiO2 platform and operates at a wavelength of 1.3 microm. The transmission spectrum of the sensor is measured with different ambient refractive indices ranging from n=1.33 to 1.42. A linear shift of the resonant wavelength with increasing ambient refractive index of 212 nm/refractive index units (RIU) is observed. The sensor detects a minimal refractive index variation of 2x10(-4) RIU.