Transmission-type terahertz beam splitter through all-dielectric metasurface

Traditional metal metasurfaces have inherent non radiative losses. In this paper, an all dielectric metasurface is proposed, which can flexibly manipulate the terahertz wave high-efficiency abnormal refraction, beam splitting and orbital angular momentum beam generation. Four kinds of elements are designed to meet the transmission phase at 0.94 THz and the phase difference is about 90°. The 2-bit coding metasurfaces are formed by periodic arrangement of these four coding units along the x-direction, and the different transmission angles can be obtained. Then two coding units with a phase difference of 180° are selected and arranged according to the requirements to achieve beam splitting effect. Finally, the coding units are arranged according to different spiral sample coding sequences to generate single and double vortex beams. It is proved that the near-field distribution and far-field scattering patterns extracted from the full wave simulation are in good agreement with the theoretical results under vertical incidence of the transverse electric-mode terahertz wave. This design provides an effective way to manipulate electromagnetic waves with high efficiency. (paper)