Tunable reflective spin-decoupled encoding metasurface based on Dirac semimetals
doi: 10.37188/CO.EN-2024-0037
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Abstract:
Multiple functional metasurfaces with high information capacity have attracted considerable attention from researchers. This study proposes a 2-bit tunable decoupled coded metasurface designed for the terahertz band, which utilizes the tunable properties of Dirac semimetals (DSM) to create a novel multilayer structure. By incorporating both geometric and propagating phases into the metasurface design, we can effectively control the electromagnetic wave. When the Fermi energy level of the DSM is set at 6 meV, the electromagnetic wave is manipulated by the DSM patch to operate at a frequency of 1.3 THz. Conversely, at a Fermi energy level of 80 meV, the electromagnetic wave is similarly controlled to function at a frequency of 1.4 THz. Both modes enable independent control of beam splitting under left-rotating circularly polarized (LCP) and right-rotating circularly polarized (RCP) wave excitation, resulting in the generation of vortex beams with distinct orbital angular momentum (OAM) modes. The findings of this study hold significant potential for enhancing information capacity and polarization multiplexing techniques in wireless communications.
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Key words:
- terahertz /
- dirac semimetal /
- spin decoupling /
- circular polarization /
- tunable
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Figure 1. (a) 3D schematic of the designed meta-atom. (b) Top view of the DSM patch in 2D. (c) Top view of the gold patch in 2D.
Figure 2. When EF = 6 meV (a) simulated reflectance spectral amplitude and phase of 8 cell parameters of gold patches at x-polarized incidence. (b) 8 meta-atoms covering a 2π phase range at 45°intervals under linearly polarized wave incidence.
Figure 3. Selected 16 meta-atoms in a 2-bit phase-modulated gold patch structure in x-polarization and y-polarization.
Figure 4. When EF = 80 meV (a) Simulated reflectance spectral amplitude and phase of 8 cell parameters of DSMs patch at x-polarized incidence. (b) 8 metaparticles covering a 2π phase range at 45°intervals under linearly polarized wave incidence.
Figure 5. Selected 16 meta-atoms in the 2-bit phase-modulated DSMs patch structure in x-polarization and y-polarization.
Figure 6. When EF = 6 meV (a, e) Vortex phase distributions for l = −2 with l = 1. (b, f) Phase distribution of gradients varying along the y-axis as well as the x-axis. (c, g) reflection coding map under LCP wave and RCP wave incidence. (d, h) 3D far-field map under LCP wave and RCP wave incidence. (i, j) 2D maps under the incidence of LCP wave and RCP wave. (k, l) vortex phases under incidence of LCP wave and RCP wave.
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