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摘要:宽频带和动态可调谐的超构表面在太赫兹无线通信、传感和医学成像等应用中具有重要的价值。结合VO 2薄膜的相变原理，本文设计了一种单层“台阶型”复合超构表面，能够实现宽频带四分之一波片和半波片之间的灵活开关功能。VO 2薄膜为常温绝缘相时，超构表面可视为透射型双偏振的宽频带四分之一波片。在1.43~2.43 THz宽频带范围内，能够将垂直入射的 x偏振光转换成左旋圆偏振光，椭圆率大于0.99，相对带宽为52%。VO 2薄膜为高温金属相时，超构表面能够实现反射型半波片功能，垂直入射的 x偏振光能够转换成 y偏振光。此外，本文也详细地研究了波片性能随倾斜入射角度的变化情况，结果表明，随着入射角度的增加，四分之一波片能够实现宽频带和双频带的动态切换，半波片可以实现频率可调谐度为57%的频移。本文所提出的单层“台阶型”复合超构表面有望促进宽频带偏振转换器件，可调谐开关和紧凑型光学器件的发展。Abstract:Dynamically tunable and broadband control of polarization is important in terahertz applications such as wireless communication, sensing, and medical imaging. We propose a single-layered “stepped” hybrid metasurface based on wire resonator and VO 2phase transition, which enables the flexible switching between broadband quarter-wave plate and half-wave plate. The hybrid metasurface is a transmission-type broadband quarter-wave plate when VO 2film is insulating phase. At 1.43~2.43 THz, it can convert the normally propagating x-polarization to left-handed circular polarization with an ellipticity over 0.99 and 52% bandwidth of the central wavelength. The hybrid metasurface can realize x- to y-polarization conversion and act as a half-wave plate when VO 2is in a metallic phase. In addition, we study the wave plate performance at different oblique incident angles. The results show that the quarter-wave plate can achieve dynamic switching between broadband and dual-band properties and the half-wave plate can achieve a frequency tunability of 57% with the increase of the incident angle. The proposed switchable terahertz qurter-/half-wave plate is expected to promote the development of broadband polarization conversion components, tunable switches and compact optical components.
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Key words:
- switchable metasurface/
- quarter-wave plate/
- half-wave plate/
- broadband/
- terahertz
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图 1基于相变原理的单层“台阶型”复合超构表面的工作原理和结构示意图。（a）VO2为绝缘相时，超构表面具有透射型四分之一波片功能；（b）VO2为金属相时，超构表面具有反射型半波片功能；（c）复合超构表面基本单元的结构参数图。
Figure 1.Schematics of structure and working principle of single-layered “stepped” hybrid metasurface based on VO2phase transition. (a) The hybrid metasurface can act as a transmission-type quarter-wave plate when VO2is in an insulating phase. (b) The hybrid metasurface is a reflection-type half-wave plate when VO2is in a metallic phase. (c) Stereogram of a unit cell in the proposed metasurface.
图 2常温下单层“台阶型”复合超构表面的透射偏振特性。（a）和（d）透射系数；（b）和（e）相位差；（c）和（f）归一化椭圆率和透射圆偏振光的能量。黄色区域带宽为1 THz，绿色区域带宽为0.22 THz。
Figure 2.Polarization performance of single-layered “stepped” hybrid metasurface when VO2film is insulating phase. (a) and (d) Transmission coefficient; (b) and (e) phase difference betweeny-andx-polarized transmitted light; (c) and (f) calculated intensityS0and ellipticityχ. The yellow area indicates the bandwidth of 1 THz, and the green area indicates the bandwidth of 0.22 THz.
图 3平行于x轴方向线栅的（a）透射特性和（b）相位差。平行于y轴方向线栅的（c）透射特性和（d）相位差。
Figure 3.(a) Simulated transmission and (b) phase difference of the wire metasurface parallelled to thex-axis direction. (c) Simulated transmission and (d) phase difference of the wire metasurface parallelled toy-axis direction
图 4温度为87°C时（x偏振光垂直入射），超构表面的反射特性和表面电流分布。（a）反射系数和偏振转换率；（b）和（c）“台阶型”金属谐振器和VO2薄膜在2.80 THz处的表面电流分布
Figure 4.At 87°C, reflection performance and surface current distribution of the hybrid metasurface underx-polarized light normal incidence. (a) Reflection coefficient and polarization conversion ratio. (b) and (c) Surface current distribution of "stepped" metal resonator and VO2film at 2.80 THz
图 5VO2相变过程中四分之一波片和半波片输出光偏振态的变化情况。（a）垂直入射x偏振光和（b）y偏振光激发超构表面产生的透射偏振态。（c）垂直入射x偏振光激发超构表面产生的反射偏振态
Figure 5.Polarization ellipse of the output wave with VO2conductivity ranging from 10 S/m to 200000 S/m. Polarization ellipse of the transmitted wave (a) at 2.20 THz forx-polarized and (b) at 2.95 THz fory-polarized normal illumination of the hybrid metasurface. (c) Polarization ellipse of the reflected wave at 2.80 THz forx-polarized normal illumination of the hybrid metasurface
图 6四分之一波片性能随入射角度的变化关系。（a）和（c）χ；（b）和（d）S0
Figure 6.Quarter-wave plate performance as a function of oblique incident angle. (a) and (c) ellipticityχ. (b) and (d) intensityS0
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[1] LIU SH, CUI T J, XU Q,et al. Anisotropic coding metamaterials and their powerful manipulation of differently polarized terahertz waves[J].Light:Science&Applications, 2016, 5(5): e16076. [2] TYO J S, GOLDSTEIN D L, CHENAULT D B,et al. Review of passive imaging polarimetry for remote sensing applications[J].Applied Optics, 2006, 45(22): 5453-5469.doi:10.1364/AO.45.005453 [3] DORRAH A H, RUBIN N A, ZAIDI A,et al. Metasurface optics for on-demand polarization transformations along the optical path[J].Nature Photonics, 2021, 15(4): 287-296.doi:10.1038/s41566-020-00750-2 [4] LAUX E, GENET C, SKAULI T,et al. Plasmonic photon sorters for spectral and polarimetric imaging[J].Nature Photonics, 2008, 2(3): 161-164.doi:10.1038/nphoton.2008.1 [5] 李天佑, 黄玲玲, 王涌天. 超颖表面原理与研究进展[J]. 中国光学,2017,10(5):523-540.doi:10.3788/co.20171005.0523LI T Y, HUANG L L, WANG Y T. The principle and research progress of metasurfaces[J].Chinese Optics, 2017, 10(5): 523-540. (in Chinese)doi:10.3788/co.20171005.0523 [6] YU N F, CAPASSO F. Flat optics with designer metasurfaces[J].Nature Materials, 2014, 13(2): 139-150.doi:10.1038/nmat3839 [7] LIU ZH CH, LI ZH CH, LIU ZH,et al. Single-layer plasmonic metasurface half-wave plates with wavelength-independent polarization conversion angle[J].ACS Photonics, 2017, 4(8): 2061-2069.doi:10.1021/acsphotonics.7b00491 [8] XIA R, JING X F, GUI X C,et al. Broadband terahertz half-wave plate based on anisotropic polarization conversion metamaterials[J].Optical Materials Express, 2017, 7(3): 977-988.doi:10.1364/OME.7.000977 [9] ZHAO Y, ALÙ A. Manipulating light polarization with ultrathin plasmonic metasurfaces[J].Physical Review B, 2011, 84(20): 205428.doi:10.1103/PhysRevB.84.205428 [10] LIU D M, LV T T, DONG G H,et al. Broadband and wide angle quarter-wave plate based on single-layered anisotropic terahertz metasurface[J].Optics Communications, 2021, 483: 126629.doi:10.1016/j.optcom.2020.126629 [11] CONG L Q, XU N N, GU J Q,et al. Highly flexible broadband terahertz metamaterial quarter-wave plate[J].Laser&Photonics Reviews, 2014, 8(4): 626-632. [12] SHI ZH J, ZHU A Y, LI ZH Y,et al. Continuous angle-tunable birefringence with freeform metasurfaces for arbitrary polarization conversion[J].Science Advances, 2020, 6(23): eaba3367.doi:10.1126/sciadv.aba3367 [13] ZHU Y H, VEGESNA S, ZHAO Y,et al. Tunable dual-band terahertz metamaterial bandpass filters[J].Optics Letters, 2013, 38(14): 2382-2384.doi:10.1364/OL.38.002382 [14] 霍红, 延凤平, 王伟, 等. 基于超材料的太赫兹高灵敏度传感器的设计[J]. 中国 ,2020,47(8):0814004.doi:10.3788/CJL202047.0814004HUO H, YAN F P, WANG W,et al. Terahertz high-sensitivity sensor design based on metamaterial[J].Chinese Journal of Lasers, 2020, 47(8): 0814004. (in Chinese)doi:10.3788/CJL202047.0814004 [15] LUO J, SHI X ZH, LUO X Q,et al. Broadband switchable terahertz half-/quarter-wave plate based on metal-VO2metamaterials[J].Optics Express, 2020, 28(21): 30861-30870.doi:10.1364/OE.406006 [16] ZHANG Y, FENG Y J, ZHU B,et al. Switchable quarter-wave plate with graphene based metamaterial for broadband terahertz wave manipulation[J].Optics Express, 2015, 23(21): 27230-27239.doi:10.1364/OE.23.027230 [17] 付亚男, 张新群, 赵国忠, 等. 基于谐振环的太赫兹宽带偏振转换器件研究[J]. 物理学报,2017,66(18):180701.doi:10.7498/aps.66.180701FU Y N, ZHANG X Q, ZHAO G ZH,et al. A broadband polarization converter based on resonant ring in terahertz region[J].Acta Physica Sinica, 2017, 66(18): 180701. (in Chinese)doi:10.7498/aps.66.180701 [18] RAO Y F, PAN L, OUYANG CH M,et al. Asymmetric transmission of linearly polarized waves based on Mie resonance in all-dielectric terahertz metamaterials[J].Optics Express, 2020, 28(20): 29855-29864.doi:10.1364/OE.404912 [19] HAN ZH L, OHNO S, TOKIZANE Y,et al. Off-resonance and in-resonance metamaterial design for a high-transmission terahertz-wave quarter-wave plate[J].Optics Letters, 2018, 43(12): 2977-2980.doi:10.1364/OL.43.002977 [20] 葛栋森, 许全, 魏明贵, 等. 基于曲折线型介质超材料的宽带太赫兹四分之一波片[J]. 红外与 工程,2017,46(9):0921002.doi:10.3788/IRLA201746.0921002GE D S, XU Q, WEI M G,et al. Broadband terahertz quarter wave plate based on meander-line dielectric metamaterials[J].Infrared and Laser Engineering, 2017, 46(9): 0921002. (in Chinese)doi:10.3788/IRLA201746.0921002 [21] LI ZH CH, LIU W W, CHENG H,et al. Realizing broadband and invertible linear-to-circular polarization converter with ultrathin single-layer metasurface[J].Scientific Reports, 2016, 5: 18106.doi:10.1038/srep18106 [22] AKO R T, LEE W S L, BHASKARAN M,et al. Broadband and wide-angle reflective linear polarization converter for terahertz waves[J].APL Photonics, 2019, 4(9): 096104.doi:10.1063/1.5116149 [23] MA SH J, WANG X K, LUO W J,et al. Ultra-wide band reflective metamaterial wave plates for terahertz waves[J].EPL(Europhysics Letters) , 2017, 117(3): 37007.doi:10.1209/0295-5075/117/37007 [24] MA ZH J, HANHAM S M, GONG Y D,et al. All-dielectric reflective half-wave plate metasurface based on the anisotropic excitation of electric and magnetic dipole resonances[J].Optics Letters, 2018, 43(4): 911-914.doi:10.1364/OL.43.000911 [25] ZEGHDOUDI T, KEBCI Z, MEZEGHRANE A,et al. Half-wave plate based on a birefringent metamaterial in the visible range[J].Optics Communications, 2021, 487: 126804.doi:10.1016/j.optcom.2021.126804 [26] ZHAO X G, SCHALCH J, ZHANG J D,et al. Electromechanically tunable metasurface transmission waveplate at terahertz frequencies[J].Optica, 2018, 5(3): 303-310.doi:10.1364/OPTICA.5.000303 [27] LEE S, KIM W T, KANG J H,et al. Single-layer metasurfaces as spectrally tunable terahertz half- and quarter-waveplates[J].ACS Applied Materials&Interfaces, 2019, 11(8): 7655-7660. [28] WANG D CH, ZHANG L CH, GONG Y D,et al. Multiband switchable terahertz quarter-wave plates via phase-change metasurfaces[J].IEEE Photonics Journal, 2016, 8(1): 5500308. [29] WANG D CH, ZHANG L CH, GU Y H,et al. Switchable ultrathin quarter-wave plate in terahertz using active phase-change metasurface[J].Scientific Reports, 2015, 5: 15020.doi:10.1038/srep15020 [30] JI Y Y, FAN F, WANG X H,et al. Broadband controllable terahertz quarter-wave plate based on graphene gratings with liquid crystals[J].Optics Express, 2018, 26(10): 12852-12862.doi:10.1364/OE.26.012852 [31] PENG L, LI X F, JIANG X,et al. A novel THz half-wave polarization converter for cross-polarization conversions of both linear and circular polarizations and polarization conversion ratio regulating by graphene[J].Journal of Lightwave Technology, 2018, 36(19): 4250-4258.doi:10.1109/JLT.2018.2836904 [32] YU X Y, GAO X, QIAO W,et al. Broadband tunable polarization converter realized by graphene-based metamaterial[J].IEEE Photonics Technology Letters, 2016, 28(21): 2399-2402.doi:10.1109/LPT.2016.2596843 [33] ZHANG Y, FENG Y J, ZHAO J M. Graphene-enabled tunable multifunctional metamaterial for dynamical polarization manipulation of broadband terahertz wave[J].Carbon, 2020, 163: 244-252.doi:10.1016/j.carbon.2020.03.001 [34] BRAND G F. The strip grating as a circular polarizer[J].American Journal of Physics, 2003, 71(5): 452-456.doi:10.1119/1.1539099 [35] GRADY N K, HEYES J E, CHOWDHURY D R,et al. Terahertz metamaterials for linear polarization conversion and anomalous refraction[J].Science, 2013, 340(6138): 1304-1307.doi:10.1126/science.1235399 [36] LIU M, XU Q, CHEN X Y,et al. Temperature-controlled asymmetric transmission of electromagnetic waves[J].Scientific Reports, 2019, 9(1): 4097.doi:10.1038/s41598-019-40791-4 [37] MARKOVICH D L, ANDRYIEUSKI A, ZALKOVSKIJ M,et al. Metamaterial polarization converter analysis: limits of performance[J].Applied Physics B, 2013, 112(2): 143-152.doi:10.1007/s00340-013-5383-8 [38] WANG J, CHEN Y T, HAO J M,et al. Shape-dependent absorption characteristics of three-layered metamaterial absorbers at near-infrared[J].Journal of Applied Physics, 2011, 109(7): 074510.doi:10.1063/1.3573495 -
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