Huygens metasurface based on glide-symmetric ELC resonator for highly efficient wavefront formation in sub-terahertz bands.

Abstract

Terahertz waves exhibit highly directional behavior and are easily blocked by obstacles, so for them to be used for wireless communications, they require a technology that can construct arbitrary propagation paths. A Huygens metasurface is a promising technology for this purpose because it can achieve bending of electromagnetic waves by applying a phase distribution to the wavefront using two-layer metal cells that provide a full (2π) phase shift range by adjustment of their geometry. However, the unit cells of Huygens metasurfaces tend to be large, with a quantized phase distribution that less accurately represents the ideal continuous phase distribution for beamforming and thus degrades diffraction efficiency. Here, we propose a glide-symmetric Huygens metasurface that is based on electric LC resonators with a much smaller unit cell than a given wavelength, in which the split parts are offset by a certain distance. We describe the design methodology and experimentally demonstrate large deflection angles up to 50° by using a metasurface having a phase distribution with a quantization number of six. The proposed structure is useful for forming arbitrary propagation paths in terahertz-band communication systems.