Fano-like resonances in the binary elliptical nanoring resonator array

Abstract

In this paper, we design and investigate a binary elliptical nanoring resonator array on a gold conducting layer, which can generate two optical Fano-like resonant modes in the visible light range under normal incidence. The gold conducting layer underneath the nanoring resonator array strongly enhances the coupling and hybridization among different resonant modes. These two distinct Fano-like resonances originate from the interactions of dipolar antibonding and bonding modes, and dipolar bonding and propagating surface plasmon modes, respectively, which provide as high a refractive index sensitivity as 620 nm/RIU, and achieve high figures of merit, 78 and 154, separately in a refractive index range of 1.33~1.40. Compared to the circular nanoring array, the elliptical structure we demonstrate here can generate shaper resonant modes that can be used for high sensitivity measurement. The designed binary elliptical nanoring resonator array is very promising for dual-channel biosensing application.