Multi-channel narrow bandstop filter and refractive index sensor based on nanodisk arrays and Fabry–Perot resonant cavities

High-performance resonant metasurfaces are promising for various applications, such as filtering and optical sensing. In this paper, a metasurface array composed of a periodically arranged nanodisk array and a Fabry-Perot (F-P) resonant cavity exhibits multiple ultra-narrow reflection resonance peaks in the near-infrared wavelength band, with a minimum bandwidth of 10 nm and the lowest reflectance of 0.08%. The number of resonant channels can also be further increased by breaking the symmetric structure. At the same time, this structure has characteristics such as polarization insensitivity. In addition, the metasurface array exhibits high sensitivity to the refractive index of the media layer, with a refractive index sensing sensitivity of over 900 nm/RIU. These advantages give the metasurface array great potential for sensing, detection, filtering, and other applications.