Terahertz Dynamic Beam Steering Based on Graphene Coding Metasurfaces

Abstract

Coding metasurfaces incorporated with reconfigurable elements can dynamically control electromagnetic waves to realize reconfigurable multiple functionalities. The mostly existing active devices usually work in microwave band and have little ability to dynamically control terahertz waves. Here, a graphene-based coding metasurface (GBCM) is presented to realize dynamic beam steering for terahertz waves. The coding state "1" of the proposed GBCM can be continuously tuned to "0" by Fermi level of an integral graphene film. In order to verify the working principle, two examples are designed to demonstrate the dynamic tunability of the proposed GBCM for terahertz waves. One is dynamic multi-beam switching and another is dynamic diffusion switching. Under the normal illumination of terahertz waves, a 1D periodic-sequence GBCM produces dual-, tri-and single-beam by setting Fermi level as 0.05 eV, 0.15 eV and 0.70 eV, respectively. Similarly, a 2D periodic-sequence GBCM produces quad-, penta-and single-beam by setting Fermi level as 0.05 eV, 0.11 eV and 0.70 eV, respectively. In the case of aperiodic coding sequence, reflected waves can be dynamically switched from diffusion to mirror reflection by increasing Fermi level from 0.05 eV to 0.70 eV. The above functionalities are well verified by theoretical calculations and numerical simulations.

Terahertz Reconfigurable Intelligent Surfaces (RISs) for 6G Communication Links

“…To have full 360 • phase coverage for dynamic-gradient phase control, graphene was designed with resonant structures (Figure 5f) [73,74] or combined with resonant metallic patterns [75,76]. A graphene-based coding metasurface for beam splitting was proposed by controlling the Fermi level (Figure 5g) [77][78][79][80][81]. Such coding metasurfaces also have great potential to be applied to security systems for message transmission [81].…”

Reduction of Radar Cross Section by Adopting Symmetrical Coding Metamaterial Design for Terahertz Frequency Applications

“…In the double layer structure category, the proposed coding metamaterial has the smallest design, while the work of [ 26 ] constructed it with a slightly bigger design, likely 200 µm × 100 µm reconfigurable metasurface. Meanwhile, the monolayer designs such as those in [ 27 , 28 ] possess a compact structure compared with the rest of the designs. In each research work, the authors successfully investigated by adopting a specific metamaterial type for desired applications.…”

“…The bistatic scattering patterns of this analysis are tabulated in Table 7. Table 8 illustrates the comparison of a few research works in terahertz frequency regimes that adopt types of metamaterial or metasurface for example [25][26][27][28]. All the research works utilised a frequency range below 5 THz and have distinct sizes.…”

Terahertz Multiple Beam Steering Using Graphene Pancharatnam-Berry Metasurfaces

“…When Fermi level of graphene changes dynamically from 0 eV to 0.3 eV, the structure changes from absorption state to reflection state. In 2021, Xu et al proposed dynamic beam steering in terahertz band based on graphene coding metasurface [32]. Dynamic beam switching and diffusion switching were realized by changing Fermi level of graphene from 0.01 eV to 0.7 eV.…”

“…x direction are calculated by (1) and (2)[32],where phase changes of the first metasurface are α x = π ( D x = 4p) along x direction and α y = 0 ( D y = ∞)along y direction, respectively. Wavelength is λ = 250 μm (1.2 THz) and period is p = 80 μm.…”