Multiple Fano Resonances Control in MIM Side-Coupled Cavities Systems

We theoretically demonstrate a plasmonic waveguide that allows easy control of the fano profile. The proposed structure is analyzed by the coupled-mode theory and demonstrated by the finite-element method. Due to the interaction of the local discrete state and the continuous spectrum caused by the side-coupled cavity and the baffle, respectively, the transmission spectrum exhibits a sharp and asymmetric profile. The profile can be easily tuned by changing the parameters of the structure. Moreover, the compact structure can easily be extended to several complex structures to achieve multiple fano resonances. These characteristics offer flexibility in the design of the device. This nanosensor yields a sensitivity of 1280 nm/RIU and switches with an on/off contrast ratio of about 30 dB. Our structures may have potential applications for nanoscale optical switching, nanosensors, and slow-light devices in highly integrated circuits.