High-sensitivity refractive index sensors based on Fano resonance in a metal-insulator-metal based arc-shaped resonator coupled with a rectangular stub

A metal-insulator-metal (MIM)-based arc-shaped resonator coupled with a rectangular stub (MARS) structure is proposed. This structure can generate two tunable Fano resonances originating from two different mechanisms. The structure has the advantage of being sensitive to the refractive index, and this feature makes it favorable for application in various microsensors. The relationship between the structural parameters and Fano resonance is researched using the finite element method (FEM) based on the software COMSOL Multiphysics 5.4. The simulation reveals that the sensitivity reaches 1900 nm/refractive index unit (RIU), and the figure of merit (FOM) is 23.75.     

Wideband slow light achievement in MIM plasmonic waveguide by controlling Fano resonance

In this paper, we have investigated the characteristics of an asymmetric shaped Fano line in a metal–insulator–metal (MIM) plasmonic waveguide side coupled to two resonating stub structures. The spectral properties of Fano resonance are quite distinct due to the destructive interference between a two propagating plasmon modes. Two structural parameters are carefully adjusted: physical separation between both the resonating stubs and length of resonating stubs. By tailoring the separation between both the resonating structures, coupling between both the plasmon modes is controlled, and hence asymmetric nature of Fano line can be shaped accordingly. Resonance condition of Fano line can be tuned by scaling the length of stubs. A strong red shift in resonating wavelength with varying degree of asymmetry is observed, when length of resonating structures is increased. The sharp resonant peak, due to an asymmetric shaped Fano resonance is generally accompanied by large dispersion that results in reduction of group velocity of light near Fano resonance. By controlling the coupling between resonating stub, or by scaling the length of lower resonating stub, large value of group index (n_g = 75) and delay bandwidth product (DBP = 0.2533) is obtained. The structure can be modified to suit different applications in optical buffers, optical switches and nonlinear optics devices.     

基于十字连通形环形谐振腔金属-介质-金属波导的折射率传感器和滤波器

提出了由十字连通形环形谐振腔耦合两个金属-介质-金属(metal-insulator-metal, MIM)波导的结构,并用有限元法数值研究了表面等离极化激元在结构中的传输特性.通过对透射谱的研究,系统地分析了MIM结构的传感特性.结果表明,在透射光谱中有三个共振峰,即存在三种共振模式,其中透射峰与材料的折射率呈线性关系.通过对结构参数的优化,得到了折射率灵敏度(S)高达1500 nm/RIU的理论值,相应的传感分辨率为1.33×10~(-4)RIU.更重要的是,灵敏度不受结构参数变化的影响,这意味着传感器的灵敏度不受制造偏差的影响.此外,谐振波长与环形腔中心半径成线性关系,该器件在较大波长范围内实现可调谐带通滤波.透射强度随着波导与环形腔间距的增大而减小,透射带宽同时减小,因此,可以通过控制环形腔与波导的耦合距离来调谐透射强度及透射带宽.研究结果对高灵敏度纳米级折射率传感器和带通滤波器的设计以及在生物传感器方面的应用都具有一定的指导意义.     

Refractive index sensing of double Fano resonance excited by nano-cube array coupled with multilayer all-dielectric film

We propose a hybrid structure of a nano-cube array coupled with multilayer full-dielectric thin films for refractive index sensing.In this structure,discrete states generated by two-dimensional grating and continuous states generated by a photonic crystal were coupled at a specific wavelength to form two Fano resonances.The transmission spectra and electric field distributions of the structure were obtained via the finite-difference time-domain method.We obtained the optimal structural parameters after optimizing the geometrical parameters.Under the optimal parameters,the figure of merit(FOM)values of the two Fano resonances reached 1.7×10⁴and 3.9×10³,respectively.These results indicate that the proposed structure can achieve high FOM refractive index sensing,thus offering extensive application prospects in the biological and chemical fields.     

Refractive index sensing by using Fano resonance enhanced two‐photon luminescence

Utilizing three‐dimensional vectorial electromagnetic simulation, we propose a new refractive index sensing mechanism based on Fano resonance enhanced two‐photon‐absorption induced luminescence (TPL). The TPL from gold nanodisk heptamer (GNDH), which is affected by the refractive index of surrounding material, is used as an example to demonstrate the sensing mechanism facilitated by Fano resonance. The sensitivity of our method is about one order of magnitude better than the conventional refractive index sensing strategy employing plasmonic Fano resonance, while the size of the sensing probe can be further reduced at the same time.

     

枝节直波导与开口方环耦合谐振腔的Fano谐振特性研究

本文构建了一个枝节直波导与带开口方环耦合谐振腔.基于金属-绝缘体-金属结构的Fano谐振原理,采用有限元法分析了该波导结构的透射谱线对谐振腔结构参数的依赖关系.在开口方环与直波导间距G=90 nm,枝节高度H=140 nm时,该谐振腔结构中可以产生中心波长分别为λ=746 nm和1521 nm具有反对称线型的双重Fano共振透射峰.研究表明：左侧谐振峰值先随H增高而升高,至H=140 nm达到最大值,之后随H增高峰值缓慢减弱,直至消失.右侧谐振峰值则几乎不受H变化影响.传输谷受H影响最大,随着H增大,枝节谐振腔的传输谷向长波长方向移动,而右侧两个传输谷基本保持不变.当H=210 nm时,左边Fano谐振完全消失,只剩下右边的谐振,且谐振峰基本保持不变.设置参数化扫描,观测Fano谐振的变化,在波长1500 nm～1700 nm之间,设置最佳参数,经拟合计算得到该谐振耦合腔可以作为一个灵敏度S为1496 nm/RIU,FOM=60.1的折射率传感器.该结构可以为纳米级折射率传感器设计提供有效依据.     

Fano resonance sensing based on coupled sub-wavelength dielectric grating and periodic photonic crystal

Based on the diffraction effect of sub-wavelength dielectric grating and the optical property of periodic photonic crystal, a hybrid structure of sub-wavelength grating all-dielectric multilayer thin film containing periodic photonic crystal is proposed. The transmission property of the structure is simulated by finite element method (FEM). The result shows that the discrete state generated by the sub-wavelength waveguide grating will be coupled with the continuous state generated by the photonic crystal cavity and the Fano resonance can be formed. The Fano resonance sensing model based on structural parameters and resonance wavelength are established, the influence of structural parameters on the Fano resonance spectral curve is quantitatively analyzed by numerical simulations, and the dynamic detection of the refractive index of samples is realized. The above structure can realize the optical refractive index sensing with high figure of merit (FOM) value and provide an effective theoretical reference for the formation of Fano resonance in the all-dielectric hybrid structure.     

基于耦合开口方环共振空腔的可控法诺共振研究

基于表面等离子激元理论与金属-介质-金属波导结构提出一个由开口方环共振空腔、挡板及MIM波导组成的波导结构,并使用有限元方法系统地研究了该结构的透射特性.仿真计算结果表明:该结构可以产生法诺共振现象,其共振波长可以通过改变开口方环空腔的长度及开口大小进行调节,该结构敏感度可达1 600nm/RIU,品质因数为1.31×10~5.此外,通过调整方环共振空腔上开口的位置,在波导中产生了双重法诺共振现象,其敏感度可达1 700nm/RIU,品质因数为8.3×10~4.该结构有望在光学集成回路,尤其是纳米生物传感器方面得到比较广泛的应用.     

Liquid refractive index sensor based on slow light in slotted photonic crystal waveguide

A high sensitive and compact refractive index sensor based on slotted photonic crystal waveguide (S-PhCW) is demonstrated. This design is worked on a Mach–Zehnder interferometer (MZI) configuration with S-PhCW as the measuring arm, which can be used to detect any changes in refractive index that correspond to different concentration of the measuring liquid. Combining the slow light enhancement in photonic crystal waveguide (PhCW) with the advantage of excellent optical confinement in slot waveguide, the sensitivity of this simple scheme can reach to 2.3 × 10⁹ nm/RIU with the active region of only 1 mm long.     

混合溶液折射率对局域表面等离子体共振的影响

对水-二甲基亚砜二元混合溶液质量分数和温度与折射率的关系进行了理论和实验研究,对几种经典模型的拟合结果进行了比较,给出了适合水-二甲基亚砜混合溶液的经验公式。对水性金溶胶-二甲基亚砜混合溶液质量分数和温度对局域表面等离子体共振峰值波长的影响进行了理论和实验研究,结果表明:水性金溶胶-二甲基亚砜混合溶液质量分数对共振峰值波长的调节有较好的线性关系和较大的调节范围,当温度从20 ℃增大到60 ℃,混合溶液金溶胶的共振峰值波长增加了1367 pm,温度敏感度为34 pm/K,在0%~100%的质量分数范围内,混合溶液金溶胶的共振峰值波长平均产生8.5103 pm的增长。     

混合溶液折射率对局域表面等离子体共振的影响

对水-二甲基亚砜二元混合溶液质量分数和温度与折射率的关系进行了理论和实验研究,对几种经典模型的拟合结果进行了比较,给出了适合水-二甲基亚砜混合溶液的经验公式。对水性金溶胶-二甲基亚砜混合溶液质量分数和温度对局域表面等离子体共振峰值波长的影响进行了理论和实验研究,结果表明：水性金溶胶-二甲基亚砜混合溶液质量分数对共振峰值波长的调节有较好的线性关系和较大的调节范围,当温度从20 ℃增大到60 ℃,混合溶液金溶胶的共振峰值波长增加了1367 pm,温度敏感度为34 pm/K,在0%~100%的质量分数范围内,混合溶液金溶胶的共振峰值波长平均产生8.5103 pm的增长。     

Enhanced Raman scattering based on fabry‐perot like resonance in a metal‐cladding waveguide

A liquid‐core metal‐cladding waveguide structure of millimeter scale is designed to enhance Raman signal via the excitation of Fabry–Perot‐like resonance. Theoretically, an oscillating field distribution covering the whole guiding layer is generated by the multireflection at the two metal interfaces. The large detection area covers the whole sample chamber because of the oscillating nature of excited high order modes with concentrated intensity. By adding metal nanoparticles, the Fabry–Perot‐like resonance can be combined with local surface plasmons resonance to further enhance the light‐matter interaction with the target molecules, which is also confirmed by the experimental results. Copyright © 2015 John Wiley & Sons, Ltd.     

基于折射率变化的一种新型盐度测量原理研究

研制了一种用于测量海水盐度的新装置。基于表面等离子共振技术,根据盐溶液折射率与盐度的关系原理,实现对盐度测量。结构中使用一只K9玻璃制成的棱镜为衬底,在棱镜的一边淀积一层厚度为55nm的Ag膜,在Ag膜上设置待测盐溶液样品池和参考池。在白光的激励下,在Ag膜中发生表面等离子共振现象。盐溶液的折射率不仅与盐的质量分数有关,且与温度有关,而样品池和装有蒸馏水的参考池具有相同温度,用两者共振波长差的变化来反映盐度,克服了温度对测量结果的影响,理论分析和实验结果验证了设计的可行性。     

基于偏振特性对石英玻璃和绿漆涂层的反演

物质的偏振特性与其复折射率、表面粗糙度以及观测几何条件有关,为了应用偏振探测技术实现对目标的定量反演,本文首先对两种典型目标(绿漆涂层和石英玻璃)的偏振特性进行了实验测定,并对偏振度与探测天顶角的关系进行了分析。利用实验数据并基于描述目标偏振特性的PG模型首次在考虑了粗糙度的影响下,对目标的折射率、消光系数进行了定量反演,最后将反演结果与参考结果进行比较。结果表明,石英玻璃的折射率相对误差为4.944 9%,绿漆涂层的折射率与消光系数的相对误差分别为11%和21.558 9%。该方法在考虑表面粗糙度的条件下能够更精确地测定物质的复折射率,同时也为偏振技术应用于目标定量反演提供了依据。     

基于辅助电介质层的棱镜表面等离子体共振效应研究

研究了一种基于棱镜基底-辅助电介质层-金膜-待测介质四层结构的表面等离子体共振(surface plasmon resonance,SPR)效应激励模型.采用薄膜光学与波导理论,探索了由辅助电介质层与金膜复合而成共振薄膜对SPR效应的激励机理与调制特性.借助时域有限差分方法,数值模拟得到辅助电介质层属性与共振能量传输特性关系.在此基础上,构建了波长调制型棱镜辅助电介质层结构SPR激励系统.研究结果表明,当待测介质折射率相同时,相较基于棱镜基底-金膜-待测介质三层结构的Kretschmann激励模型,辅助电介质层激励模型共振光谱整体向长波方向偏移且半波宽度出现显著展宽效应.而当待测介质折射率增大时,辅助电介质层型激励模型的共振光谱不仅会向长波方向偏移,而且折射率响应灵敏度比棱镜Kretschmann三层激励模型高出75%.因此该模型能够为诸如高灵敏度检测、新型光学滤波与调制器件设计等领域的研究应用提供理论与实践储备.     

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.     

基于超材料吸波体的低雷达散射截面波导缝隙阵列天线

提出利用超材料吸波体减缩波导缝隙阵列天线带内雷达散射截面的设计方法. 设计具有超薄(厚度仅为0.01λ, λ为吸波体中心频率对应波长)、无表面损耗层和高吸波率的超材料吸波体, 将其加载到波导缝隙天线E面方向辐射缝隙间的金属表面上, 并与辐射缝隙保持一定的间距. 该加载方式没有破坏天线的口径馈电振幅分布, 并利用超材料吸波体对电磁波的强吸收特性降低了天线阵的结构模式项散射. 仿真和实验结果表明, 加载超材料吸波体后天线阵的反射系数、增益、波瓣宽度保持不变, 在x极化和y极化条件下, 波导缝隙阵列天线的带内雷达散射截面减缩量均在6 dB 以上, 且在-25°-+25°范围内天线雷达散射截面均有明显的减缩, 鼻锥方向减缩超过10 dB. 该研究成果对阵列天线雷达散射截面减缩具有重要的借鉴意义和工程应用价值.     

契形结构光纤表面等离子体共振传感器研究

提出了一种契形端面结构的光纤表面等离子体共振(SPR)传感器激励模型. 采用时域有限差分法对契形SPR波导的共振模型进行数值模拟, 通过在光纤出射端抛磨契形角度并进行敏感膜修饰, 制出具有契形端面结构的类Kretschmann微棱镜式光纤SPR传感器, 实现激发SPR的光波调制.结果表明, 在1.3330–1.4215折射率范围内, 制备的契形光纤SPR传感器相对于常规光纤SPR传感器, 其平均灵敏度提高了近1–6倍, 1倍和6倍分别出现在小角度结构(15° 契形) 传感器和大角度结构(60°契形) 传感器, 且仍保持 10^-5 等级的分辨率. 该类型结构的传感器具有契形端面激励模式, 设计灵活性高、制备工艺简单、可微量检测样本等优点, 能够很好地适应于不同环境和测量条件的实际生化检测、环境监测需求. 关键词： 光纤传感器 表面等离子体共振 契形端面结构 折射率灵敏度     

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...     

小型化多层双模基片集成波导平衡带通滤波器

针对平衡滤波器小型化和高选择的应用需求,提出两种新型的多层双模基片集成波导平衡带通滤波器。首先详细分析了基于平衡端口馈电的双模基片集成波导谐振器的特性;然后根据谐振模式分布特性,设计了一种输入输出馈线同时在上层双模谐振器上的四阶平衡带通滤波器,下层双模谐振器通过十字交叉槽线结构与上层谐振器耦合,可以实现三个传输零点;又提出一种输入和输出馈线分别在上层和下层双模谐振器上的四阶平衡带通滤波器,上层和下层谐振器通过一个槽线进行耦合,可以实现两个对称的传输零点。基于提出的两种平衡滤波器结构,分别设计了一个中心频率为10 GHz的平衡带通滤波器,并进行加工和测试。测试和仿真结果一致性较好,表明了该结构可以实现小型化和高选择,并且具有很好的共模抑制特性。