High-sensitivity Fano resonance refractive index sensor based on a MIM plasmonic structure coupled with two resonators

Abstract In this article, we present a refractive index (RI) sensor based on Fano resonance that exploits the interaction between a nanoring resonator and a metal–insulator–metal (MIM) waveguide. Our structure consists of a coupling between a waveguide and two resonators: one in the form of a ring and the other of lateral type. The nano-ring resonator is formed by two half-ring segments that are coupled to the MIM waveguide. The transmission spectrum of the proposed coupled system reveals a distinct Fano-type resonance that responds sensitively to variations in the surrounding RI. The sensor demonstrates an estimated sensitivity of about 3200 nm RIU −1 , which is higher than that of other Fano resonance–based sensors reported in the literature. The sensor’s simple structural design facilitates fabrication and enables its use in numerous RI detection applications.