Compact Terahertz Dielectric Folded Metasurface

Abstract Despite modern terahertz (THz) systems benefit from the developments in metasurfaces with flexible wavefront manipulation capabilities, the large propagation space between the THz source/detector and metasurface component, as well as the inherent insertion loss of metasurfaces, are the two main bottlenecks that hinder metasurface‐based THz devices from becoming a practical technology. This article addresses these two problems by demonstrating a compact, high‐efficiency folded metasurface system in the THz band. The device comprises two parallel dielectric metasurfaces, between which the THz waves are confined to reduce the system volume. The bottom reflective metasurface consists of an array of anisotropic dielectric resonators, which can simultaneously manipulate THz waves’ phase and polarization properties. The upper metasurface is a dielectric Bragg polarizer that selects the desired linear polarization of THz waves to pass through. Low‐loss and nondispersive high‐resistivity silicon is used as the material for both metasurfaces in this design, which is essential to achieving high efficiency. The compact and high‐efficiency folded THz metasystem is further experimentally verified. The introduced folded device can be used in diverse applications such as high‐speed THz communications, non‐destructive detection, and imaging systems, significantly reducing their volume and increasing their radiation efficiency.