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中国物理学会期刊

太赫兹多波束调控反射编码超表面

CSTR: 32037.14.aps.72.20221962

Terahertz multibeam modulation reflection-coded metasurface

CSTR: 32037.14.aps.72.20221962
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  • 已报道的大多数编码超表面仅利用相位或幅度编码进行电磁波调控, 限制了太赫兹波调控灵活性. 本文提出了一种反射超表面单元, 通过相位编码构造超表面, 在圆极化波入射下获得反射波束分裂和偏转功能, 实现对圆极化波束的灵活调控; 同一超表面单元结构利用幅度编码构造超表面在线极化太赫兹波入射下, 实现空间成像功能. 通过相位编码和幅度编码结合构造超表面, 提高了对太赫兹波操控的灵活性, 该编码超表面构造思路可以为太赫兹器件设计提供一种全新思路.

     

    Most of reported coding metasurfaces only use phase encoding or amplitude encoding to regulate electromagnetic waves, which limits the flexibility of terahertz wave regulation. In this work, a metasurface element structure is proposed. The metasurface element is composed of three layers, i.e. metal pattern structure layer, intermediate medium layer, and metal base layer. According to the geometric phase principle, the phase coverage in the 2π range can be achieved by rotating the metal pattern structure layer under the incidence of the circular-polarized terahertz wave. The metasurface element structure is arranged reasonably by using the phase coding, and the 1-bit and 2-bit phase coding metasurface are designed. First of all, the coding metasurface with interlacing “0” and “1” is designed to generate a double beam reflection under the vertical incidence of circular polarized terahertz waves, while the two-dimensional checkerboard coding metasurface with “0” and “1” generates a symmetrical four-beam reflection. In addition, the metasurface is designed to deflect the reflected beam, and the coding period is changed to design the metasurface to deflect the reflected beam to the specified angle, showing good flexibility. Finally, the convolutional operation is introduced to flexibly regulate the circular polarized beam, and the functions of beam splitting and reflection beam deflection are obtained. The amplitude coded metasurface is designed under theincidence of the online polarized terahertz wave, and the near-field imaging effect can be realized by the amplitude differentiation of polarization reflection. The designed amplitude coded metasurface realizes the function of imaging in space, presenting the designed “CJLU” pattern, which has different imaging effects at different observation locations. When the observation plane distance is 80 μm at the observation frequency of 1.22 THz, the near-field imaging effect is best. In conclusion, we propose a terahertz multibeam modulation reflection-coded metasurface, which combines geometric phase and amplitude variation to achieve different terahertz wave modulation functions under different polarization incident terahertz waves. The results from the simulated near-field radiation model and the far-field radiation model are both in agreement with the theoretical calculation predictions. The designed metasurface provides a degree of freedom method for terahertz wave polarization and phase manipulation, which greatly improves the efficiency of terahertz wave manipulation and has potential applications in terahertz systems.

     

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