Independently controllable multiple Fano resonances in side-coupled MDM structure and its applications for sensing and wavelength demultiplexing

Tunable single and multiple Fano resonances are investigated theoretically and numerically in a plasmonic structure, which consists of a cavity (or cavities) side-coupled with a defective metal-dielectric-metal (MDM) waveguide. The results show the Fano resonances originate from the interference between discrete states and a continuum state. These Fano resonances can be independently tuned by adjusting the corresponding cavity parameters. This structure can be utilized to achieve ultrasensitive plasmonic sensor yields with a sensitivity of 1400 nm/RIU. The highest figure of merit (FOM) similar to 1.75 x 10(4) is obtained by optimizing structure. Furthermore, compact and high wavelength resolution plasmonic 1 x 2 and 1 x 3 wavelength demultiplexers based on Fano resonances are designed and investigated. This compact and flexible structure has significant applications for sensing, switching, wavelength selecting, as well as constructing highly integrated optical circuits and complex waveguide networks.