Dual-Mode Surface Lattice Resonances in Asymmetric Optical Metasurfaces for Refractive Index Sensing

This paper demonstrates dual-mode reflection-type surface lattice resonances (SLRs) in two kinds of asymmetric optical metasurfaces, which can be applied to refractive index sensing with a high figure of merit (FoM). The rectangular array metasurface without C
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symmetry can produce (±1,0) and (0, ±1) order SLRs concurrently in the case of natural light incidence, and corresponding FoMs can reach 29.23 and 20.05 respectively. Additionally, the asymmetric dimer metasurface excites (±1,0) and (±1, ±1) order SLRs with FoMs of 37.42 and 24.38. The dual SLRs can be designed regularly and flexibly by tuning period lengths or establishing dimer meta-atoms, which provides a promising candidate for the next commercially available sensors.