基于狄拉克半金属的可调谐反射自旋解耦编码超表面
Tunable reflective spin-decoupled encoding metasurface based on Dirac semimetals
doi: 10.37188/CO.EN-2024-0037
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摘要:
具有较高信息容量的多功能超表面受到研究者的广泛关注。本文提出了一种基于太赫兹波段的2位可调谐解耦编码超表面，利用狄拉克半金属(DSM)的可调谐特性设计了一种新的多层结构，在超表面结构中引入几何相位和传播相位，可以有效地调控电磁波。当DSM的费米能级为6 mev时，电磁波由DSM贴片控制，在1.3 THz这一频点工作，当费米能级为80 mev时，电磁波由嵌在DSM薄膜上的金贴片控制，在1.4 THz这一频点工作，这两种模式都可以在左旋圆极化(LCP)波和右旋圆极化(RCP)波激励下实现轨道角动量(OAM)模式不同的涡旋波束的独立控制。这项工作为提高信息容量和无线通信中极化复用技术带来巨大潜力。
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 with 80 meV, the electromagnetic wave is manipulated by the DSM patch with the gold patch embedded in the DSM film, operating at a frequency of 1.3 THz and 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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