Generation of terahertz vortex beams base on metasurface antenna array
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摘要: 为了研究1阶和2阶模式下的非连续性相位L型天线的超表面阵列特性，采用异常透射的散射场理论，设计了一种L型天线结构，控制天线的几何参量，选取阵列单元组，使得其覆盖相位超过2π。并根据不同的拓扑荷，设计1阶和2阶涡旋相位板，产生不同阶数涡旋光束。结果表明，用太赫兹线偏光垂直入射时，天线单元垂直偏振透射方向的模拟仿真效率达到55%左右；相位覆盖0~2π和0~4π时，其线性阵列的异常透射角不同，分别为-14.7°和-30°，其结果与广义斯涅耳定理一致。此研究对太赫兹涡旋光束的器件研究有重要的应用价值。Abstract: In order to study characteristics of metasurface array of discontinuous phase L-shaped antenna in the 1st and 2nd order modes, by using the theory of scattering field with anomalous transmission, a L-shaped antenna structure was designed. By controlling the geometric parameters of the antenna and selecting the array element group, the coverage phase exceeded 2π. According to different topological charges, the vortex phase plates of the 1st order and the 2nd order were designed to produce different order vortex beams. The simulation results show that the simulation efficiency of the vertical polarization direction of the antenna element is about 55% when the incident wave is polarized vertically. When the phase covered 0~2π and 0~4π, the anomalous transmission angles of the linear array are different, -14.7° and -30° respectively. The results are consistent with the generalized Fresnel theory. This study has the important application value in the research of terahertz vortex beam devices.
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Keywords:
- scattering /
- terahertz /
- metasurface /
- anomalous transmission /
- vortex beam
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Figure 1. a—2-D graph of L-shaped antenna unit b—3-D map of L-shaped antenna unit c—the scattering amplitude of single L-shaped antenna unit with the change of h and r d— the scattering phase of single L-shaped antenna unit with the change of h and r
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Figure 2. a—the overlay phase array: array A(2π) and array B(2×2π) b—the normalized amplitude and phase diagram of the polarized light vertically
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Figure 3. a—the 1st order transmission spectrum parallel to the polarization direction of incident light b—the 1st order transmission spectrum perpendicular to the polarization direction of incident light c— the 2nd order transmission spectrum parallel to the polarization direction of incident light d—the 2nd order transmission spectrum perpendicular to the polarization direction of incident light
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Figure 4. a—vortex phase plate under topological charge l=1 b—the normalized amplitude under topological charge l=1 c—the vortex phase under topological charge l=1 d—vortex phase plate under topological charge l=2 e—the normalized amplitude under topological charge l=2 f—the vortex phase under topological charge l=2
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