Manipulation of Terahertz Wave Based on Three-Layer Transmissive Pancharatnam-Berry Phase Metasurface

Abstract

In order to improve the transmitted efficiency of metasurfaces, the three-layer unit cell structure with coupling characteristics between layers was proposed. Using these Pancharatnam-Berry phase element particles with three-layer structure, we constructed encoded metasurfaces with different sequences to control the transmitted scattered waves. However, the manipulation of continuous transmission angle requires the continuous change of encoding metasurface period. Since the size of encoding particles in the coded metasurfaces cannot be designed to be infinitesimally small, it is impossible to obtain the continuously changing period of coded metasurfaces. In order to obtain the continuous manipulation of transmission scattering angles, we introduced the principle of Fourier convolution operation in digital signal processing on encoding metasurface sequences. By performing the addition and subtraction operation between two different encoding metasurface sequences, a new encoding metasurface sequence can be obtained with different scattering angle. The transmission scattering angles can be obtained continuously, and the terahertz wave can be manipulated freely. Moreover, by using the proposed three-layer highly efficient Pancharatnam-Berry phase encoding meta-atoms, these coded particles with different rotation angles can be precisely arranged to build the generators of the orbital angular momentum beam with different topological charges.