Wideband near-zero-index metamaterials created by using a supercell microstructure in the terahertz range

Abstract

Zero-index metamaterials are widely used in electromagnetic devices due to their favorable optical properties such as infinite large-phase velocity and quasi-infinite wavelength. However, insufficient bandwidth and high loss seriously limit the wide application of zero refractive index metamaterials (ZIMs), especially in the terahertz band. Here, we propose a kind of supercell microstructure metamaterial to realize a broadband near-zero refractive index. This new superlattice structure contains four subunit structures of different sizes in a single unit. Dual broadband characteristics of the near-zero refractive index can be demonstrated in our design. The bandwidth of the near-zero index can reach about 30 GHz with low loss. The resonance principle of the supercell microstructure and the generation mechanism of the near-zero refractive index are discussed in detail. The influence of the thickness of the medium, of the thickness of the metal sheet, and of the period of the central area and the metal line width on the near-zero refractive index is analyzed. Dual broadband zero-refractive metamaterials bring wider applications to various optoelectronic devices for arbitrary wavefront conversion, directional radiation, and obstacle-free light guiding.