太赫兹介质超表面实现双域多信道复用

Ling, 王羚 Wang; Feng, 高峰 Gao; Shuhua, 滕书华 Teng; Zhiguo, 谭志国 Tan; Xing, 张星 Zhang; Jun, 娄军 Lou; Li, 邓力 Deng

doi:10.3788/aos221337

Cited by 2 publications

(1 citation statement)

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“…随着太赫兹电磁超材料功能器件的发展，已经在通信、成像、生物检测等诸多领域展现出广阔的应用前景 [1][2][3][4][5][6] 。而随着多场景应用需求的增加，迫切希望此类器件具有多种功能且能够工作于多个频段 [7][8][9][10] 。超表面作为二维形式的电磁超材料，具有低剖面、低损耗、高效率等优点。 2014 年，在超表面的基础上， "编码超表面"的概念 [11] 提出，通过数字化控制手段，实现了对电磁波的高效调控，大大降低了超表面功能器件的设计难度，成为了研究的热点。但是，一般的编码超表面一旦设计完成，其功能也随之固定，无法满足多场景应用的需求。为了解决上述问题，主要采用三种方式设计多功能编码超表面：1、使编码超表面可在多个工作频点，进而设计不同功能 [12][13][14] 。这类编码超表面一般需要设计多层结构或将不同结构合理地嵌套组合，使其在不同工作频点分别产生谐振响应。2、引入特定的结构(例如：对正交线极化(Linearly Polarized, LP)波中的 x 和 y 极化波分别独立调控的各向异性十字结构 [15] ；对左旋圆极化(Left-Circularly Polarized, LCP)波和右旋圆极化 (Right-Circularly Polarized, RCP) 波分别独立调控的自旋解耦结构 [16] ) ，使编码超表面在不同极化态的波源入射时 [15][16][17] ，表现出不同的功能。3、将可调材料 [18][19][20][21] (石墨烯、液晶、相变材料等)引入编码超表面的设计中，实现不同功能的切换。特别地，二氧化钒(VO 2 )作为一种相变材料，具有相变方式灵活，加工制备简单等优势，被广泛地应用于太赫兹可调功能器件的设计中 [22] ，典型的结构如 Li 等 [20]…”

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Vanadium dioxide based terahertz dual-frequency multi-function coding metasurface

Jing-Li¹,

Dong²,

Liang³

et al. 2023

Acta Phys. Sin.

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Terahertz (THz) wave has the advantages of low photon energy, high resolution, large communication bandwidth, etc. It has broad application prospects in security detection, high-resolution imaging, high-speed communication and other fields. In recent years, as a new way to control THz wave, THz metasurface functional devices have attracted extensive attention of researchers. In this paper, vanadium dioxide (VO2), a phase change material, is introduced into the coding metasurface. By regulating a circularly polarized wave and the orthogonal linearly polarized waves independently, a multi-function coding metasurface that can work at dual frequency points is obtained. It is composed of three layers. The top layeris a metal-VO2 composite structure. The middle is a polyimide dielectric layer. The bottom is a metal ground. Under certain conditions, the double split ring resonator (DSRR) and the cross structure in the top layer are relatively independent. Designing the coding sequences for them separately can enable the coding metasurface to have multiple functions. The electromagnetic simulation software CST is used for modeling and simulation, and the results are as follows. When the VO2 is in an insulating state and a circularly polarized wave at 0.34 THz is incident vertically, the characteristics of coding metasurface elements are mainly affected by the DSRR. The DSRR is rotated to meet the requirements of 3-bit Pancharatnam-Berry phase coding. The coding sequence is designed to generate vortex beams with the topological charge l=± 1 at a specific angle. The VO2’s state is changed to a metallic state, the DSRR can be equivalent to a metal ring. When the orthogonal linearly polarized waves at 0.74 THz are incident vertically, the characteristics of coding metasurface elements are mainly affected by the cross structure. Because of its anisotropy, four different 2-bit coding metasurface elements can be obtained respectively by changing the length of the horizontal arm and the vertical arm. The design of appropriate coding sequences can realize the radar cross section reduction of the x-polarized wave and the beam splitting of the y-polarized wave, and the results have broadband characteristics. Multiple coding sequences can be designed by specialcharacteristics of the coding metasurface, then various expected functions can be realized on the same metasurface. To a certain extent, it solves the problem of single function of ordinary metasurface devices, and paves a novel way to the development of THz multi-function systems.

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