Electromagnetic multipole resonance-driven metasurface for high-performance multi-channel refractive index sensing in the near-infrared.

Metasurfaces with the remarkable ability to regulate electromagnetic waves play an increasingly important role in optical and optoelectronic systems. In this study, we theoretically propose a metasurface consisting of four fan-shaped nanorod periodic arrays, which achieves multi-channel near-infrared absorption via electromagnetic multipole resonances. Simultaneously, the effects of structural parameters on the spectral absorptance are investigated, and four near-perfect absorption peaks are obtained after optimization. Furthermore, as a proof-of-concept, the refractive index (RI, n) sensor driven by the metasurface is used to identify analytes (n=1.00-2.00), multi-channel detection peaks offer potential for the RI sensing robustness. Meanwhile, the maximum sensitivity (S), figure of merit (FOM), and quality factor (Q) of the designed RI sensor at the four peak wavelengths reach 1056.3 nm/RIU, 389.8RIU-1, and 1088.5, respectively. In addition, the multi-channel absorption and RI sensing concept can be extended to a cuboid nanorod geometry, further demonstrating the robustness of the designed metasurface. The four-channel detection and outstanding RI sensing performance provide a possible way toward ultrasensitive detection with metasurfaces.