Refractive index sensor based on Fano resonance in a ring with a rectangular cavity structure

Abstract

This paper presents an innovative plasmonics-based refractive index sensor structure that consists of a circular ring containing a rectangular cavity (CRRC) and a metal–insulator–metal (MIM) waveguide with two rectangular stubs. The narrowband mode of the CRRC interacts with the broadband mode of the bus waveguide stub to generate sharp and asymmetric Fano resonance. The transmission characteristics were simulated using the finite element method. A maximum refractive-index sensor sensitivity of 2300 nm/RIU and figure of merit (FOM) of 57.5 were achieved. The proposed structure is simple yet highly sensitive and has the potential to be useful in detecting electrolyte concentration in blood. The results of this study provide a foundation for developing highly sensitive plasmonic sensors biomedical applications.