A Refractive Index Nanosensor Based on Fano Resonance in the Plasmonic Waveguide System

Abstract

A novel and compact refractive index sensor based on Fano resonance in the plasmonic waveguide system, which comprises with a stub and groove resonator coupled with a metal–insulator–metal waveguide, is proposed and investigated by the finite-element method. Due to the interaction of the narrow discrete resonance and a broad spectrum caused by the stub resonator and the groove, respectively, the transmission spectrum exhibits a sharp asymmetrical profile. Simulation results show that the Fano resonance can be easily tuned by changing the parameters of the structure. These characteristics offer flexibility to design the devices. This nanosensor yields a sensitivity of $\sim 1260$ nm/RIU and a figure of merit of $\sim 2.3\,\times \, 10^{\mathrm {\mathbf {4}}}$ . This letter is significant for design and application of the sensitive nanoscale refractive index sensor.