Design of Transmissive Terahertz Beam Splitter based on Phase Gradient Metasurface

Abstract

In this paper, we present a bi-directional beam splitter and a four-directional beam splitter made of the phase gradient metasurface. The unit cells are composed of two L-shaped metallic layers, and which are sandwiched by dielectric layer between them. By especially designing the arm length and width of the L-shaped unit and arranging them according to the Berry phase principle, th phase variation of <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$0\sim 2\pi$</tex> has been obtained. A <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$12^{\ast}12$</tex> bi-directional beam splitter and a <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$16^{\ast}16$</tex> four-directional beam splitter are formed by periodic arrangement of such unit cells. When the splitter is vertically incident by linear polarized plane wave at 100 GHz, the deflection angle is about 30°, which shows consistency with the theoretical design. Compared with the traditional beam splitters designed with prisms and interference gratings, these two beam splitters have the advantages of low profile, compact, and ease to be loaded into micro-nano optical devices.