Refractive Index Sensing Based on Multiple Fano Resonances in a Split-Ring Cavity-Coupled MIM Waveguide

A metal–insulator–metal (MIM) waveguide consisting of a circular split-ring resonance cavity (CSRRC) and double symmetric rectangular stub (DSRSW) is designed, which can excite quadruple Fano resonances. The finite element method (FEM) used to investigate influences geometric parameters on the transmission characteristics structure. results show that resonances are excited by interference between DSRSW CSRRC. Among them, wavelengths tuned narrow-band discrete state CSRRC, line transmittance profiles wide-band continuous DSRSW. sensitivity (S) be up 1328.8 nm/RIU, figure merit (FOM) 4.80 × 104. Based these advantages, structure has potential applications in sensing sub-wavelength range.