Multi-band metamaterial absorber with arbitrary polarization and wide-incident angle

We propose a multi-band metamaterial perfect absorber with a deep-subwavelength thickness and near-unity absorption coefficient at microwave frequencies. This planar metamaterial is composed of periodically arranged concentric metallic rings and a continuous metallic ground plate separated by one or two lossy dielectric layers. The origin of the induced multi-band perfect absorption is attributed to the multiple impedance-matching to free space and can be achieved through tuning the effective constitutive relations by interactions of several electromagnetic resonances. Numerical simulations reveal the electric field and surface current distributions at each absorption peak, and further analysis indicates that the absorption mainly arises from the dielectric loss. Moreover, the absorption could be enhanced and broaden by overlapping the modes of different rings. The absorption is identical for arbitrary polarizations due to the rotational symmetry of the subwavelength unit. It also remains over 90% energy absorption for a wide angle of incidence up to 45∘\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$^\circ$$\end{document}, which is confirmed by the experiment. The designed multi-band absorber is also easy to manufacture by the mature printed circuit board technology, which is favorable for a wide variety of applications.