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.

Resonance characteristics of independently tuned dual Fano of metal-dielectric-metal waveguide coupling square cavity with double baffles

A metal-dielectric-metal (MDM) waveguide coupling two square cavities with double baffles is designed in this paper based on the transmission characteristics of surface plasmon polaritons in subwavelength structure. The independent tuning of the dual Fano resonance is implemented by the interference between the wide-spectrum mode generated by the F-P (Fabry Perot) cavity and the two narrow-spectrum modes generated by the two square cavities. Moreover, the independent tuning of the dual Fano resonance can be achieved by changing the sizes of the two square cavities and filling medium. The coupled-mode theory (CMT) is adopted to analyze the transmission characteristics of the dual Fano resonance. The structure is simulated by the finite element method to quantitatively analyze the influence of structural parameters on the independent tuning of the dual Fano resonance and the refractive index sensing characteristics. The proposed sensor yields respectively sensitivity higher than 1020 nm/RIU and 1120 nm/RIU and a figure of merit of 3.29×10⁵ and 1.17×10⁶ by optimizing the geometry parameters. This structure provides an effective theoretical reference in the optical integration of ultra-fast optical switches, multi-function high-sensitivity sensors and slow-light devices.