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

Abstract

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

A dual-purpose sensor with a sawtooth U-shaped cavity and a rectangle-shaped cavity in a MIM waveguide structure

“…As can be seen from equation (5), the resonant wavelength of the waveguide coupled cavity (λ res ) is affected by the effective refractive index (n eff ) and effective length (l p ) of the resonator [41][42][43][44][45]. Under the same structural parameters, the effective refractive index remains unchanged.…”

A Nanoscale Structure Based on an MIM Waveguide Coupled with a Q Resonator for Monitoring Trace Element Concentration in the Human Body

“…The S value at this point is 2260 nm/RIU. Its performance was better than most of the parameters in Table 1 [28][29][30][31]. If the angle changes and the structure changes, will there be different propagation characteristics?…”

“…The S value at this point is 2260 nm/RIU. Its performance was better than most of the parameters in Table 1 [28][29][30][31]. Subsequently, we studied the effect of geometric parameters L and H on system performance.…”

Refractive Index Sensor Based on a Metal-Insulator-Metal Bus Waveguide Coupled with a U-Shaped Ring Resonator

“…The silver was chosen as the filling metal, which is due to its higher electric field and lower power consumption. The relative permittivity of air is 1, and the relative permittivity of silver can be acquired using the Debye–Drude dispersion model: where represents the angular frequency of the light, can be expressed as the plasma frequency of silver, and is the relaxation time [ 25 , 26 ].…”