Polarization-insensitive and polarization-controlled dual-band absorption in metamaterials

We numerically and experimentally investigated dual-band absorption of sandwich-structure metamaterials which include periodic metal coupled rings at the front separated from the metal plane at the back by a dielectric layer. The properties are demonstrated in both GHz and mid-IR regimes of electromagnetic (EM) wave. The dual-band perfect absorber with polarization independence is observed under normal incidence. In order to understand the EM properties of dual-band perfect absorber, the plasmonic excitation was clarified for both peaks. Finally, by connecting the rings, the perfect-absorption peaks can be controlled with the polarization angle of incident EM wave.