Tunable sharp resonances based on multimode interference in a MIM-ring coupling plasmonic resonator system

An asymmetric plasmonic resonator system is composed of two metal-insulator-metal (MIM) waveguides and a ring resonator is proposed. And tunable sharp resonance based on multimode interference in MIM-ring coupling plasmonic resonator system is theoretically and numerically studied. The Fano resonance of the two different physical mechanisms in this paper is explained by using the multimode interference coupled mode theory (MICMT). Results obtained by the theory of MICMT are very well consistent with those from the finite element method (FEM) simulation. For an independent MIM-ring coupling plasmonic resonator system, its Fano resonance is formed by different resonance modes of the same ring resonator interfering with each other. Moreover, the theory of ring resonator explains the red shift which is attributable to the increase of the inner ring radius. For the rectangular and ring hybrid coupling plasmonic resonator system, the electromagnetic waves in the ring resonator and the rectangular resonator interfere with each other, which leads to the Fano resonance. We also studied the sensitivity (S) and figure of merit (FOM) of the rectangular and ring hybrid resonator system as a refractive index sensor up to 1350 nm /RIU and 1543, respectively, which has a certain reference value for the bio-chemical sensors, filters and modulator for large-scale photonic integration