Multiple Fano Resonance Based Optical Refractive Index Sensor Composed of Micro-Cavity and Micro-Structure

Abstract

A multiple Fano resonance based optical refractive index sensor composed of micro-cavity and micro-structure is designed. The multiple Fano resonances, generated by the interference between the multiple resonant peaks produced by the micro-cavity and the continuous background produced by the micro-structure, can reach high sensitivity in refractive index measurement. Besides, the micro-cavity configuration obviously reduces the energy loss, thus effectively increasing the figure of merit. Adjusted by the micro-cavity thickness and the micro-structure configuration, multiple Fano resonances can be generated potential for refractive index sensing: the sensitivity of 831 nm/RIU and the figure of merit of $\sim$600 can be reached according to a single Fano resonance; moreover, spectral interval between double Fano resonances can also be used for refractive index sensing with the sensitivity of 194 nm/RIU but significantly reducing the error due to the environmental changes. Considering the advantages as high sensitivity, narrow Fano resonant peak, high figure of merit and ease of integration, as well as its potential in environmental error reduction, the proposed multiple Fano resonance based optical refractive index sensor is expected to provide new tactics for optical refractive index sensing.