Terahertz Metasurface: Non-Diffracting OAM Generation, Multidimensional Multiplexing, and SA-RCS Reduction

Abstract

In this article, we propose a metasurface element with a simple structure and diverse functions. Then, the polarization properties of metasurface elements were looked at, and simulations using the finite element method (FEM) were used to get the surface current and electric field distribution, which was confirmed by transmission line theory (TLT). Based on the Pancharatnam-Berry (PB) phase method, the 3-bit coded metasurface and 10 gradient phase metasurface elements were designed. Therefore, design can produce maximum non-diffracting distance d _max = 1055.265 μm non-diffracting on orbital angular momentum (OAM), and design the incidence angle for θ_i ( f ₁ ) = 27.22°, θ_i ( f ₂ ) = 31.54°, and θ_i ( f ₃ ) = 24.25°, corresponding to the frequency respectively f ₁ = 2.62 THz, f ₂ = 2.29 THz, and f ₃ = 2.93 THz, respectively along the − x , − y , x and y direction incidence, corresponding respectively along the + z axis coaxial topological charge of l ₁ = 4, l ₂ = −1, l ₃ = 2 mode of l ₄ = −2 the OAM vortex beam, which implements the 3 × 4 = 12 coaxial orthogonal OAM of the OAM mode, frequency, and angle multiplexing metasurface, realises multidimensional reuse, and the multiplexing channel is uncapped in theory. The aforementioned observation is closely tied to the fundamental property that OAM modes exhibit orthogonality to one another. Furthermore, this study also examines the methodology and concept of the simulated annealing algorithm (SA) in relation to optimizing the application of radar cross section (RCS) reduction.