Multiband selective absorbers made of 1D periodic Ag/SiO₂/Ag core/shell coaxial cylinders horizontally lying on a planar substrate.

In this paper, we present a one-dimensional periodic microstructure for multiband selective absorbers of thermal radiation. The microstructure is made of Ag/SiO₂/Ag core/shell coaxial cylinders horizontally lying on top of a SiO₂ dielectric spacer and an opaque silver substrate. The spectral-directional absorptivity of the proposed structure was numerically investigated with the finite element based Comsol Multiphysics software. Multiband selective absorption in the wavenumber range from 2500 to 20000 cm^-1 for TM-wave incidence was obtained. Physical mechanisms responsible for the multiband selective absorption were elucidated due to the resonance of magnetic polaritons in the SiO₂ spacer shell, excitation of surface plasmon polaritons at the SiO₂/Ag interface, and the effect of Wood's anomaly. Furthermore, the effects of a silver core radius, spacer shell thickness, a confocal elliptical core/shell cylinder on the property of multiband absorption, and the absorptivity of the structure with one core/four shells coaxial cylinders were explored.