Numerical investigation of metasurface narrowband perfect absorber and a plasmonic sensor for a near-infrared wavelength range

Herein, we have presented a computation study of a metasurface (MS) narrowband perfect absorber performed utilizing the three-dimensional finite element method. In the first part of the paper, the periodic sequence of silicon meta-atoms (MAs) is positioned on a ∼100 nm gold thin-film. The gold thin-film obstructs a broadband light at normal incidence, and silicon MAs are utilized to stimulate the surface plasmon by scattering light through it. The highest absorption of 96% is procured at 930.26 nm in the air medium which can be further enhanced by using a layered structure of MAs deposited on gold. The MAs are composed of Si/SiO₂/Si with an optimized layers height. Consequently, the perfect impedance matching of the electric and magnetic dipoles takes place providing a 99% of absorption insensitive to the incidence angle of light and almost negligible reflection at a resonating wavelength of 889.4 nm. This feature allows us to utilize this device as a plasmonic sensor. That is why, in the second part of the paper, the proposed device design is studied for the detection of the refractive index of the surrounding medium. The sensitivity and figure of merits of the MS device are in the range of 460–492 nm RIU⁻¹ and 76.7–82 RIU⁻¹, respectively. We claim that the anticipated MS element can be employed in solar photovoltaic and biomedical sensing purposes. (paper)