A Terahertz gradient metasurface based on hybridized dipole andquadrupole resonances

Abstract

Metasurfaces have demonstrated a wide range of functions, including guided scattering and localization of electromagnetic waves, and they are a promising platform for replacing bulk components in the Terahertz frequency range. Nevertheless, precise local control of the scattered wave on a very subwavelength scale remains a challenge, with high magnitude and full 2p phase tuning being difficult to achieve with a single resonance structure. Here we present a simple deeply subwavelength (l=16) metamaterial unit cell based upon the coupling of dipole and quadrupole resonances, which achieves complete phase coverage as well as high reflection magnitude. We numerically demonstrate high efficiency anomalous reflection (81%) at an angle of 45, avoiding almost all other spurious diffraction orders (0:15%). We also design a structure with a lower reflection angle of 25, where efficiency is expected to degrade due to the presence of higher order Floquet modes. However, we observe that efficiency remains high ( 85%) with 0:58% spurious reflections. Hence, our design can be used in a variety of applications such as beam forming and scanning antennas, reflectarray antennas, phase shifters and beam splitters.