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提出了一种基于双开缝环结构的半反射和半透射双偏振超宽带太赫兹超表面, 能实现光束偏折和生成涡旋光束. 该超表面单元结构仅由附着在超薄介质层上的金属双开缝环构成, 在超宽频带范围内同时调控反射和透射太赫兹圆偏振(circular polarization, CP)波和线偏振( linear polarization, LP)波. 基于传输相位和几何相位理论, 改变开缝环的大小和旋转方向, 在0.3—1.2 THz范围内可以实现透射和反射的正交LP波和CP波在0—2π相移全覆盖, 对应的正交LP波和CP波平均幅值为0.45的相对带宽分别达到86%和120%. 本文特别设计了全空间超表面模型, 实现了LP波和CP波光束偏折与生成涡旋光束. 这些研究有助于全空间多功能太赫兹超表面器件的实现和实际应用.In this paper, we propose a dual-polarization ultra-wideband metasurface with half-reflection and half-transmission based on a double-split-ring (DSR) structure operating in a terahertz (THz) frequency range. The designed metasurface can simultaneously control the circularly polarized (CP) wave and linearly polarized (LP) wave in reflection mode and transmission mode, covering an extensive THz frequency range. The unit-cell architecture of the metasurface consists of a periodic arrangement of the DSR structure made of metal, which is affixed to an ultra-thin dielectric substrate. By manipulating the size and rotation direction of the DSR structure, we achieve full phase coverage of 0–2π of the orthogonally polarized LP wave and CP wave across a frequency span of 0.3–1.2 THz, encompassing transmission and reflection scenarios. The relative bandwidths of the corresponding orthogonal LP wave and CP wave with an average amplitude of 0.45 reach 86% and 120%, respectively. Specifically, through numerical simulations, we demonstrate that the designed metasurface has the ability to achieve THz beam deflection and vortex beam generation while reflecting and transmitting LP wave and CP wave. The proposed dual-polarization ultra-wideband metasurface holds great promise for various applications in the terahertz frequency range. These findings pave the way for the development of flexible and versatile THz devices with expanded functionality, thereby opening up new possibilities for wavefront manipulation in metasurfaces.
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Keywords:
- terahertz /
- metasurface /
- circular polarization /
- linear polarization /
- beam deflection /
- vortex beam
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Liu J Q, Cheng Y Z, Chen F, Luo H 2023 Infrared Laser Engineer. 52 20220377
Google Scholar
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图 1 MS示意图 (a), (b)单元结构前视图和透视图; LPy波垂直入射下在(c) 0.4 THz, (d) 0.8 THz和(e) 1.1 THz处单元结构表面电流分布
Fig. 1. Schematic diagram of MS: (a), (b) Front and perspective view of the unit-cell structure; the surface current distributions of the unit-cell structure under the normal incident LPy wave at (c) 0.4 THz, (d) 0.8 THz and (e) 1.1 THz.
图 2 入射LP波和CP波通过单层MS转化成正交偏振波的(a1), (c1)反射系数(rxy, ryx, r–+, r+–)和(b1), (d1)透射系数(txy, tyx, t–+, t+–)以及(a2)—(d2)对应的相位
Fig. 2. Reflection coefficient (rxy, ryx, r–+, r+–) (a1), (c1) and transmission coefficient (txy, tyx, t–+, t+–) (b1), (d1) of the orthogonal polarization wave for the normal incident LP wave and CP wave through the designed single-layer MS, and the corresponding phase (a2)–(d2).
图 3 在0.5 THz, 8个不同单元结构的(a), (c)反射和透射(b), (d)正交LP和CP波的幅值和相位 (a), (b) LP波; (c), (d) CP波; 插图是一个具有(a), (b)传输相位和(c), (d)几何相位梯度分布的8个不同单元MS超单元结构
Fig. 3. Amplitude and phase of the (a), (c) reflected and (b), (d) transmitted orthogonal LP and CP waves for 8 different unit-cells at 0.5 THz: (a), (b) LP wave; (c), (d) CP wave. The inset shows a supercell of the MS with 8 unit-cells with gradient distributions of (a), (b) propagation phase and (c), (d) geometric phase.
图 4 (a), (b)在0.5 THz 时异常反射和折射的LP波在x-z平面电场分布; (c), (d)对应的归一化强度
Fig. 4. (a), (b) Simulated electric field distributions of the abnormal reflection and refraction orthogonal LP wave in the x-z plane at 0.5 THz, and (c), (d) the corresponding normalized intensity.
图 5 (a), (b)在0.8 THz时异常反射和折射的CP波在x-z平面中的电场分布; (c), (d)对应的归一化强度
Fig. 5. (a), (b) Simulated electric field distributions of the abnormal reflection and refraction orthogonal CP wave in the x-z plane at 0.8 THz, and (c), (d) the corresponding normalized intensity.
图 6 仿真得到的不同频率下正交LP波和CP波的(a), (c)反射角和(b), (d)折射角 (a), (b) LP波; (c), (d) CP波; 虚线是对应的理论计算得到的依赖于频率的正交LP和CP波反射和折射角
Fig. 6. Simulated (a), (c) reflection and (b), (d) refraction angles of the orthogonal LP waves and CP waves via different frequencies: (a), (b) LP waves; (c), (d) CP waves. Dash lines indicate the theoretical calculation frequency-dependent reflection and refraction angles of the orthogonal LP and CP waves.
图 7 所提出的生成不同OAM拓扑电荷涡旋光束的单层MS补偿相位分布 (a) l = +1; (b) l = –1; (c) l = +2; (d) l = –2
Fig. 7. Compensating phase distribution of the proposed single-layer MS for the generated vortex beam with different OAM topological charges: (a) l = +1; (b) l = –1; (c) l = +2; (d) l = –2.
图 8 在0.8 THz垂直入射的LP波通过设计的单层MS后拓扑电荷数为(a1)—(a4) l = +1, (b1)—(b4) l = –1, (c1)—(c4) l = +2, (d1)—(d4) l = –2的反射和透射涡旋光束的电场强度分布和对应的OAM模式纯度分布 (a1)—(d1)反射涡旋光束的电场强度分布; (a2)—(d2)透射涡旋光束的电场强度分布; (a3)—(d3)反射涡旋光束的OAM模式纯度分布; (a4)—(d4)透射涡旋光束的OAM模式纯度分布
Fig. 8. Electric field intensity and the corresponding OAM mode purity distributions of the reflected and transmitted vortex beams with a topological charge of (a1)–(a4) l = +1, (b1)–(b4) l = –1, (c1)–(c4) l = +2 and (d1)–(d4) l = –2 for the normal incident LP wave at 0.8 THz: (a1)–(d1) Electric field intensity of reflected vortex beams; (a2)–(d2) electric field intensity of transmitted vortex beams; (a3)–(d3) OAM mode purity distributions of reflected vortex beams; (a4)–(d4) OAM mode purity distributions of transmitted vortex beams.
图 9 在0.4 THz垂直入射的CP波通过设计的单层MS后拓扑电荷数为(a1)—(a4)l = +1, (b1)—(b4) l = –1, (c1)—(c4) l = +2和(d1)—(d4) l = –2的反射和透射涡旋光束电场强度分布和对应的OAM模式纯度分布 (a1)—(d1)反射涡旋光束的电场强度分布; (a2)—(d2)透射涡旋光束的电场强度分布; (a3)—(d3)反射涡旋光束的OAM模式纯度分布; (a4)—(d4)透射涡旋光束的OAM模式纯度分布
Fig. 9. Electric field intensity and the corresponding OAM mode purity distributions of the reflected and transmitted vortex beams with a topological charge of (a1)–(a4) l = +1, (b1)–(b4) l = –1, (c1)–(c4) l = +2 and (d1)–(d4) l = –2 for the normal incident CP wave at 0.4 THz: (a1)–(d1) Electric field intensity of reflected vortex beams; (a2)–(d2) electric field intensity of transmitted vortex beams; (a3)–(d3) OAM mode purity distributions of reflected vortex beams; (a4)–(d4) OAM mode purity distributions of transmitted vortex beams.
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[1] 郝宏刚, 冉雪红, 郑森, 唐逸豪, 阮巍 2022 电子与信息学报 44 114284741
Google Scholar
Hao H G, Ran X H, Zheng S, Tang Y H, Ruan W 2022 J. Electron. Inform. Technol. 44 114284741
Google Scholar
[2] 刘靖宇, 李文宇, 刘智星, 舒敬懿, 赵国忠 2022 物理学报 71 230701
Google Scholar
Liu J Y, Li W Y, Liu Z X, Shu J Y, Zhao G Z 2022 Acta Phys. Sin. 71 230701
Google Scholar
[3] 王俊瑶, 樊俊鹏, 舒好, 刘畅, 程用志 2021 光电工程 48 200319
Google Scholar
Wang J Y, Fan J P, Shu H, Liu C, Cheng Y Z 2021 Opto-Electronic Eng. 48 200319
Google Scholar
[4] Fan J P, Cheng Y Z 2020 J. Phys. D. Appl. Phys. 53 025109
Google Scholar
[5] Yu N, Genevet P, Kats M A, Aieta F, Tetienne J P, Capasso F, Gaburro Z 2011 Science 334 33
Google Scholar
[6] He B, Liu J Q, Cheng Y Z, Chen F, Luo H, Li X C 2022 Physica E 144 115373
Google Scholar
[7] 李国强, 施宏宇, 刘康, 李博林, 衣建甲, 张安学, 徐卓 2021 物理学报 70 188701
Google Scholar
Li G Q, Shi H Y, Liu K, Li B L, Yi J J, Zhang A X, Xu Z 2021 Acta Phys. Sin. 70 188701
Google Scholar
[8] 周璐, 赵国忠, 李晓楠 2019 物理学报 68 108701
Google Scholar
Zhou L, Zhao G Z, Li X N 2019 Acta Phys. Sin. 68 108701
Google Scholar
[9] Li N, Zhao J, Tang P, Cheng Y 2023 Phys. Status Solidi B 5 2300104
[10] Cheng Y Z, Qian Y J, Luo H, Chen F, Cheng Z 2023 Physica E 146 115527
Google Scholar
[11] Liu M, Huo P, Zhu W, Zhang C, Zhang S, Song M, Zhang S, Zhou Q, Chen L, Lezec H J, Agrawal A, Lu Y, Xu T 2021 Nat. Commun. 12 2230
Google Scholar
[12] Hou H S, Wang G M, Li H P, Guo W L, Cai T 2020 Opt. Express 19 27575
[13] Zhu X Z, Cheng Y Z, Chen F, Luo H, Ling W 2022 J. Opt. Soc. Am. B 39 705
Google Scholar
[14] Cai T, Wang G M, Tang S W, Xu H X, Duan J W, Guo H J, Guan F X, Sun S L, He Q, Zhou L 2017 Phys. Rev. Appl. 8 034033
Google Scholar
[15] Wu R Y, Zhang L, Bao L, Wu L W, Ma Q, Bai G D, Wu H T, Cui T J 2019 Adv. Optical Mater. 7 1801429
Google Scholar
[16] Fan J P, Cheng Y Z, He B 2021 J. Phys. D. Appl. Phys. 54 115101
Google Scholar
[17] Li J, Cheng Y Z, Li X C 2022 Adv. Theor. Simul. 5 2200151
Google Scholar
[18] Zhang C B, Wang G M, Xu H X, Zhang X, Li H P 2020 Adv. Opt. Mater. 8 1901719
Google Scholar
[19] Zhang H C, Zhang X, Ma X L, Pu M B, Huang C, Zhang Z J, Wang Y X, Guo Y H, Luo J, Luo X G 2022 Opt. Express 30 36949
Google Scholar
[20] Mao R Q, Wang G M, Cai T, Liu K, Wang D P, Wu B 2020 Opt. Express 21 31216
[21] Yang D R, Cheng Y Z, Luo H, Chen F, Wu, 2023 Adv. Theor. Simul. 4 2300162
[22] Zhao J, Li N, Cheng Y 2023 Opt. Commun. 536 129372
Google Scholar
[23] Zhao Y, Alù A 2011 Phys. Rev. B 84 205428
Google Scholar
[24] Yang L J, Li J S 2022 Opt. Eng. 61 047105
[25] Liu J Q, Cheng Y Z, Chen F, Luo H, Li X C 2023 J. Opt. Soc. Am. B 40 441
Google Scholar
[26] 刘佳琪, 程用志, 陈浮, 罗辉, 李享成 2023 红外与激光工程 52 20220377
Google Scholar
Liu J Q, Cheng Y Z, Chen F, Luo H 2023 Infrared Laser Engineer. 52 20220377
Google Scholar
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