Multi-peak electromagnetically induced transparency in concentric multiple-ring metamaterials

We theoretically and experimentally demonstrate the multi-peak electromagnetically induced transparency (EIT) phenomenon in planar multiple-ring metamaterial. The metamaterial consists of a planar array of concentric subwavelength ring resonators covering a thin dielectric substrate. Both simulation and experimental results show that the proposed metamaterial reveals low-order resonant frequencies of multiple EIT-like transparent windows insensitive to the polarization and angle of incidence of incident electromagnetic waves, and the number of EIT-like transparent windows is always equal to one less than the number of rings. The observed trapped mode resonant feature results from excitation of an antisymmetric current mode oscillating in two adjacent rings, and the polarization effect of the metamaterial near a grazing incidence is attributed to different contributions of the electric and magnetic components. The multiple-ring metamaterial promises many multi-band potential applications such as filters, slow light, sensing and nonlinear applications.