Abstract
A broadband near-perfect absorber is analyzed by an amorphous silicon (a-Si) hook shaped nanostructure metasurface. The transmission and reflection coefficients of the metasurface are investigated in the point electric and magnetic dipole approximation. By combining square and semicircle nanostructures, the effective polarizabilities of the a-Si metasurface calculated based on discrete dipole approximation (DDA) exhibit broadened peaks of electric dipole (ED) and magnetic dipole (MD) Mie resonances. The optical spectra of the metasurface are simulated with different periods, in which suppressed transmission are shifted spectrally to overlap with each other, leading to broadened enhanced absorption induced by interference of ED and MD Mie resonances. The angle insensitive absorption of the metasurface arrives 95% in simulation and 85% in experiment in spectral range from 564 nm to 584 nm, which provides potential applicability in nano-photonic fields of energy harvesting and energy collection.
Highlights
Metasurfaces are artificial planar material composed of spatially arranged subwavelength structures, which exhibit remarkable flexibility in manipulating the properties of light at an optically thin interface [1,2,3]
The broadband Mie resonances of the amorphous silicon (a-Si) hook shaped nanostructure metasurface are investigated by effective polarizabilities based on discrete dipole approximation (DDA)
The light-induced electric dipole (ED) and magnetic dipole (MD) moment of an a-Si hook shaped nanostructure in the periodical array are related with displacement currents [25]: p=− 1 iω
Summary
Metasurfaces are artificial planar material composed of spatially arranged subwavelength structures, which exhibit remarkable flexibility in manipulating the properties of light at an optically thin interface [1,2,3]. Dielectric nanostructure metasurfaces, holding advantages including nonradiative loss [11,12,13], resonant enhancement of both electric and magnetic field [14,15,16,17,18,19], attract much attention in research of high absorption induced by the Mie dipole resonances [20,21,22,23]. Yang’s group has reported a narrow band perfect absorber with a high quality factor by an amorphous silicon (a-Si) nano antenna metasurface, which is realized due to the coherent ED and MD Mie resonances and the intrinsic loss of material [23]. Liu’s group has put forward a germanium moth-eye nanostructure to obtain a perfect selective absorption attributed by the electric field enhancement due to electric and magnetic multipole resonances, which is insensitive to incident angle from 0◦ to 75◦ [24]
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