A High-Performance Refractive Index Sensor Based on Hybrid Resonance Modes in a Square Nanocavity Coupled with Metal-Insulator-Metal Plasmonic Waveguide

We present one of the simplest nanoscale systems for a high-performance refractive index (RI) sensor. We investigate analytically and numerically the transmission response of the system, which consists of the rectangular nanocavity coupled to metal-insulator-metal (MIM) nanowaveguide according to its structural parameter and resonance mode of the cavity. From the theoretical results, we find that a square cavity is able to support a hybrid resonant mode of two resonance modes with the opposite symmetry to each other. By comparison with single modes, the hybrid mode enables us to obtain ultra-low transmission response with high quality factor through the system at the resonance and it gives us possibility for realization of RI sensor with both high sensitivity and figure of merit (FoM) based on the system. And the simulation results confirm the theoretical analysis. This nanoscale sensor has a sensitivity as high as 1400nm/RIU and a FoM as large as 3000. The suggested sensor can be widely used as a high-sensitive, highly integrated sensor.

Automated summary

We present a simple nanoscale refractive index sensor system and analyze its transmission response. The system consists of a rectangular nanocavity coupled to a metal-insulator-metal nanowaveguide. Theoretical analysis reveals that a square cavity can support a hybrid resonant mode with high quality factor and low transmission response. This nanoscale sensor has high sensitivity and figure of merit.