Refractive index sensor based on multiple Fano resonances excited by MIM waveguide couplessd hexagonal nut and square ring resonators

Abstract

This study proposed a micro-nano structure capable of generating multiple Fano resonances for refractive index sensing of gases and liquids. The structure consists of a metal-insulator-metal waveguide with a baffle and two resonators, one of hexagonal nut and one of square ring. The transmission spectrum shows that the designed structure can generate up to five Fano resonances tuned by different resonators. The data obtained are fitted by multi-mode interferometric coupling mode theory, and the results are in good agreement. The sensing performance of the structure is investigated in the refractive index ranges of 1.00–1.10 and 1.30–1.40. The corresponding maximum sensitivity and maximum figure of merit are up to 998 nm/RIU and 49016, 1026 nm/RIU and 14890, respectively. The designed structure can be used as gas and liquid sensors and have great potential for micro-nasno sensing and biochemical medicine applications.