八边形腔和缺口圆环腔耦合MIM波导的Fano共振及传感特性研究  

Fano Resonance and Sensing Characteristics of MIM Waveguide Coupled with Octagonal Cavity and Notched Ring Cavity

作　　者：司珂军 白晶 王进 孟腾飞 李耀东 王莉 娄睿 Si Kejun;Bai Jing;Wang Jin;Meng Tengfei;Li Yaodong;Wang Li;Lou Rui(Department of Physics,Taiyuan Normal University,Jinzhong 030619,Shanxi,China;State Key Laboratory of Transient Optics and Photonics,Xi’an Institute of Optics and Precision Mechanics,Chinese Academy of Sciences,Xi’an 710119,Shaanxi,China)

机构地区：[1]太原师范学院物理系,山西晋中030619 [2]中国科学院西安光学精密机械研究所瞬态光学与光子技术国家重点实验室,陕西西安710119

出　　处：《光学学报》2024年第23期130-138,共9页Acta Optica Sinica

基　　金：国家自然科学基金(62075238);山西省高等学校科技创新项目(2021L421)。

摘　　要：提出一种由上方正八边形腔和下方缺口圆环腔耦合的金属-介质-金属(MIM)等离激元波导结构。入射光在金属纳米波导结构表面激发等离激元,通过八边形腔和缺口圆环腔的离散态与带金属挡板直波导的连续态发生干涉,产生Fano共振现象。采用有限元法对谐振腔单个结构参数进行研究,并根据介质前后折射率的变化对MIM波导透射率大小的影响进行分析。详细讨论八边形腔边长、缺口圆环腔半径和缺口圆环腔角度对传感器透射光谱以及品质因数(FOM)的影响。当八边形腔边长S=268 nm,缺口圆环腔半径R=268 nm,缺口圆环腔角度θ=220°时,仿真结果显示:该结构产生的三个Fano共振的FOM分别为1.6047×10^(4)、3.8852×10^(4)和1842.54,灵敏度分别为650 nm/RIU(refractive index unit)、1000 nm/RIU和1250 nm/RIU。该系统结构所具有的良好传感特性,为实现高性能微型光学传感器提供一种可行的技术方法。Objective Based on the concept of surface plasmon polaritons(SPPs),we confine the SPPs to metal or insulator interfaces through a metal-insulator-metal(MIM)waveguide.This approach breaks the classical diffraction limit and allows light to be manipulated at the nanoscale.The study of sensing characteristics by modifying the resonant cavity coupled to the straight waveguide has become a research hotspot.However,achieving optimal solutions for the transmission spectrum,sensitivity,number of peaks,and figure of merit(FOM)of the MIM waveguide coupled resonant cavities remains challenging.To meet the requirements of high sensitivity,high FOM,and multiple Fano resonance peaks for waveguide structures and optical refractive index sensors,the transmission characteristics of SPPs are deeply explored,and an innovative structural design is proposed based on this.This design features a single baffle MIM waveguide coupled with two different types of resonant cavities:an octagonal cavity above and a notched ring cavity below.The clever combination of this structure enables interference effects under near-field coupling,eliminates narrow discrete states formed by the metal baffle and wide continuous states formed by the octagonal and notched ring cavities,and results in three different modes of Fano resonance.This model not only effectively improves the sensor’s sensitivity but also significantly enhances the FOM through reasonable structural design.Different coupling paths and coupling strengths excite the three modes of Fano resonance,each exhibiting unique spectral characteristics.Methods The proposed MIM waveguide consists of a straight waveguide with a metal baffle,an upper octagonal resonant cavity,and a lower notched ring cavity.The coupling distance between the resonant cavities and the straight waveguide with the metal baffle g=10 nm.The width of the metal baffle in the straight waveguide d=20 nm.The widths of the octagonal resonant cavity,the notched ring resonant cavity,and the straight waveguide w=50 nm.The side le

关 键 词：Fano共振 表面等离激元 传感 波导 灵敏度 

分 类 号：TN256[电子电信—物理电子学]