Infrared Metasurface with a Top Cross-Square Nanobrick Array for Realizing a Highly Efficient Lightwave Absorption Across a Broad Wavelength Region

A type of metasurface with a top cross-square nanobrick (CSNB) array is proposed for realizing a highly efficient infrared (IR) radiation absorption across a broad wavelength region covering three traditional atmospheric windows. The metasurface is successfully constructed by integrating a layered CSNB array over a composite dielectric bottom supported by a common silicon substrate. The metasurface sample experimentally exhibits an average radiation absorptivity of more than 86% and a very low transmittance of less than 2% in the 1.28-14 μm wavelength region measured. A polarized absorption sensibility of the incident lightwaves and an average IR absorptivity of more than 80% with an oblique incidence at 40° are also demonstrated. The strong broad IR absorption with a negligible radiation transmission can be attributed to the existence of an obvious electromagnetic shielding action of the nanocavity formed between adjacent titanium films, and further, the near-field lightwave excitation upon the CSNBs of the metasurface charged by incident lightwaves satisfying the resonant condition needed.