Quintuple Fano-like MIM Plasmonics Structure Based On Coupling Resonators for Refractive Index Sensing

This paper mainly presents a nanoscale plasmonic structure, consisting of a waveguide with baffle, a semicircle connecting with four rectangular cavities, called tooth cavities. The whole evolution process of adding tooth cavity and adjusting parameters from the basic structure is also analyzed. Additonally, the position of the tooth cavity is independently adjustable, and the best sensing characteristic curve can be obtained by adjusting the positions of the middle two tooth cavities. Due to the coupling between the wide-spectrum resonance excited by the baffle in waveguide and narrow spectrum resonances emerging from the semicircular cavity connecting rectangular cavities, multi-Fano resonances arise in the simulation results. The transmission spectrum of the proposed structure indicates that 5 Fano peaks are generated in total, and the transmittance of the highest Fano peak can reach 0.88. The structure can be used as a refractive index sensor with a sensitivity of 1000 nm/RIU and figure of merit (FOM) of 38026 by avail of Fano resonance.