Abstract: metamaterials and metasurfaces have attracted much attention due to their powerful ability to control electromagnetic (EM) waves. In this paper, we review the recent developments in the field of EM metamaterials, starting from their exotic physics to their applications in novel information systems. First, we show the fundamental understanding on traditional metamaterials based on the effective medium theory and related applications, such as invisibility cloaks and meta-lenses. Second, we review the two-dimensional versions of metamaterials, i.e., metasurfaces, for controlling spatial waves and surface waves and thereafter present their typical designs. In particular, we briefly introduce spoof surface plasmon polaritons and their applications in microwave frequencies. Following the above approach, we emphatically present the concepts of digital coding metamaterials, programmable metamaterials, and information metamaterials. By extending the principles of information science to metamaterial designs, several functional devices and information systems are presented, which enable digital and EM-wave manipulations simultaneously. Finally, we give a brief summary of the development prospects for microwave metamaterials.

电磁超材料:从新物理现象到新信息系统

[1]Bai GD, Ma Q, Iqbal S, et al., 2018. Multitasking shared aperture enabled with multiband digital coding metasurface. Adv Opt Mater, 6(21):1800657.

[2]Bai GD, Ma Q, Cao WK, et al., 2019. Manipulation of electromagnetic and acoustic wave behaviors via shared digital coding metallic metasurface. Adv Intell Syst, 1(5): 1900038.

[3]Bao L, Ma Q, Bai GD, et al., 2018. Design of digital coding metasurfaces with independent controls of phase and amplitude responses. Appl Phys Lett, 113(6):063502.

[4]Bie X, Jing XF, Hong Z, et al., 2018. Flexible control of transmitting terahertz beams based on multilayer encoding metasurfaces. Appl Opt, 57(30):9070-9077.

[5]Cai BG, Li YB, Jiang WX, et al., 2015. Generation of spatial Bessel beams using holographic metasurface. Opt Expr, 23(6):7593-7601.

[6]Chen HS, Wu BI, Zhang BL, et al., 2007. Electromagnetic wave interactions with a metamaterial cloak. Phys Rev Lett, 99(6):063903.

[7]Chen HT, Taylor AJ, Yu NF, 2016. A review of metasurfaces: physics and applications. Rep Progr Phys, 79(7):076401.

[8]Chen K, Feng YJ, Monticone F, et al., 2017. A reconfigurable active Huygens’ metalens. Adv Mater, 29(17):1606422.

[9]Chen MLN, Jiang LJ, Sha W, 2016. Ultrathin complementary metasurface for orbital angular momentum generation at microwave frequencies. IEEE Trans Antenn Propag, 65(1):396-400.

[10]Chen X, Ma HF, Zou XY, et al., 2011. Three-dimensional broadband and high-directivity lens antenna made of metamaterials. J Appl Phys, 110(4):044904.

[11]Cheng Q, Cui TJ, Jiang WX, et al., 2010. An omnidirectional electromagnetic absorber made of metamaterials. New J Phys, 12(6):063006.

[12]Collin RE, 1960. Field Theory of Guided Waves. McGraw-Hill, New York.

[13]Cui TJ, 2017. Microwave metamaterials—from passive to digital and programmable controls of electromagnetic waves. J Opt, 19(8):084004.

[14]Cui TJ, 2018. Microwave metamaterials. Nat Sci Rev, 5(2): 134-136.

[15]Cui TJ, Smith DR, Liu R, 2010. Metamaterials: Theory, Design, and Applications. Springer, New York.

[16]Cui TJ, Qi MQ, Wan X, et al., 2014. Coding metamaterials, digital metamaterials and programmable metamaterials. Light Sci Appl, 3(10):e218.

[17]Cui TJ, Liu S, Li LL, 2016. Information entropy of coding metasurface. Light Sci Appl, 5(11):e16172.

[18]Cui TJ, Liu S, Zhang L, 2017a. Information metamaterials and metasurfaces. J Mater Chem C, 5(15):3644-3668.

[19]Cui TJ, Wu RY, Wu W, et al., 2017b. Large-scale transmission- type multifunctional anisotropic coding metasurfaces in millimeter-wave frequencies. J Phys D, 50(40):404002.

[20]Cui TJ, Liu S, Bai GD, et al., 2019. Direct transmission of digital message via programmable coding metasurface. Research, 2019:2584509.

[21]Dai JY, Zhao J, Cheng Q, et al., 2018. Independent control of harmonic amplitudes and phases via a time-domain digital coding metasurface. Light Sci Appl, 7(1):90.

[22]Ding F, Pors A, Bozhevolnyi SI, 2017. Gradient metasurfaces: a review of fundamentals and applications. Rep Progr Phys, 81(2):026401.

[23]Engheta N, Ziolkowski RW, 2006. Electromagnetic Meta- materials: Physics and Engineering Explorations. Wiley and IEEE Press, Hoboken.

[24]Fu XJ, Cui TJ, 2019. Recent progress on metamaterials: from effective medium model to real-time information processing system. Progr Quant Electron, 67:100223.

[25]Gao LH, Cheng Q, Yang J, et al., 2015. Broadband diffusion of terahertz waves by multi-bit coding metasurfaces. Light Sci Appl, 4(9):e324.

[26]Gao X, Han X, Cao WP, et al., 2015. Ultrawideband and high-efficiency linear polarization converter based on double V-shaped metasurface. IEEE Trans Antenn Propag, 63(8):3522-3530.

[27]Gao Z, Wu L, Gao F, et al., 2018. Spoof plasmonics: from metamaterial concept to topological description. Adv Mater, 30(31):1706683.

[28]Garcia-Vidal J, Martín-Moreno L, Pendry JB, 2005. Surfaces with holes in them: new plasmonic metamaterials. J Opt A, 7(2):S97-S101.

[29]Gil M, Bonache J, Martín F, 2008. Metamaterial filters: a review. Metamaterials, 2(4):186-197.

[30]Giovampaola CD, Engheta N, 2014. Digital metamaterials. Nat Mater, 13(12):1115-1121.

[31]Han JQ, Li L, Yi H, et al., 2018. 1-bit digital orbital angular momentum vortex beam generator based on a coding reflective metasurface. Opt Mater Expr, 8(11):3470-3478.

[32]Holloway CL, Kuester EF, Gordon JA, et al., 2012. An overview of the theory and applications of metasurfaces: the two-dimensional equivalents of metamaterials. IEEE Antenn Propag Mag, 54(2):10-35.

[33]Huang YJ, Wen GJ, Li J, et al., 2013. Wide-angle and polarization-independent metamaterial absorber based on snowflake-shaped configuration. J Electromagn Waves Appl, 27(5):552-559.

[34]Jiang WX, Ge S, Han TC, et al., 2016. Shaping 3D path of electromagnetic waves using gradient-refractive-index metamaterials. Adv Sci, 3(8):1600022.

[35]Jing Y, Li YF, Zhang JQ, et al., 2018. Fast coding method of metasurfaces based on 1D coding in orthogonal directions. J Phys D, 51(47):475103.

[36]Karimi E, Schulz SA, de Leon I, et al., 2014. Generating optical orbital angular momentum at visible wavelengths using a plasmonic metasurface. Light Sci Appl, 3(5): e167.

[37]Kong GS, Ma HF, Cai BG, et al., 2016. Continuous leaky- wave scanning using periodically modulated spoof plasmonic waveguide. Sci Rep, 6:29600.

[38]Kuester EF, Mohamed MA, Piket-May M, et al., 2003. Averaged transition conditions for electromagnetic fields at a metafilm. IEEE Trans Antenn Propag, 51(10):2641- 2651.

[39]Kundtz N, Smith DR, 2010. Extreme-angle broadband metamaterial lens. Nat Mater, 9(2):129-132.

[40]Landy N, Smith DR, 2013. A full-parameter unidirectional metamaterial cloak for microwaves. Nat Mater, 12(1): 25-28.

[41]Li HP, Wang GM, Gao XJ, et al., 2018. A novel metasurface for dual-mode and dual-band flat high-gain antenna application. IEEE Trans Antenn Propag, 66(7):3706-3711.

[42]Li K, Li L, Cai YM, et al., 2015. A novel design of low-profile dual-band circularly polarized antenna with meta-surface. IEEE Antenn Wirel Propag Lett, 14:1650-1653.

[43]Li LL, Cui TJ, 2019. Information metamaterials―from effective media to real-time information processing systems. Nanophotonics, 8(5):703-724.

[44]Li LL, Cui TJ, Ji W, et al., 2017. Electromagnetic reprogrammable coding-metasurface holograms. Nat Commun, 8(1):197.

[45]Li Y, Assouar BM, 2016. Acoustic metasurface-based perfect absorber with deep subwavelength thickness. Appl Phys Lett, 108(6):063502.

[46]Li Y, Liang B, Gu ZM, et al., 2013. Reflected wavefront manipulation based on ultrathin planar acoustic metasurfaces. Sci Rep, 3:2546.

[47]Li YB, Wan X, Cai BG, et al., 2014. Frequency-controls of electromagnetic multi-beam scanning by metasurfaces. Sci Rep, 4:6921.

[48]Li YB, Cai BG, Cheng Q, et al., 2016a. Isotropic holographic metasurfaces for dual‐functional radiations without mutual interferences. Adv Funct Mater, 26(1):29-35.

[49]Li YB, Li LL, Xu BB, et al., 2016b. Transmission-type 2-bit programmable metasurface for single-sensor and single- frequency microwave imaging. Sci Rep, 6:23731.

[50]Li ZC, Liu WW, Cheng H, et al., 2015. Realizing broadband and invertible linear-to-circular polarization converter with ultrathin single-layer metasurface. Sci Rep, 5:18106.

[51]Li ZC, Liu WW, Cheng H, et al., 2016. Tunable dual-band asymmetric transmission for circularly polarized waves with graphene planar chiral metasurfaces. Opt Lett, 41(13): 3142-3145.

[52]Liang LJ, Qi MQ, Yang J, et al., 2015. Anomalous terahertz reflection and scattering by flexible and conformal coding metamaterials. Adv Opt Mater, 3(10):1374-1380.

[53]Liao Z, Zhao J, Pan BC, et al., 2014. Broadband transition between microstrip line and conformal surface plasmon waveguide. J Phys D, 47(31):315103.

[54]Lin XQ, Cui TJ, Chin JY, et al., 2008. Controlling electromagnetic waves using tunable gradient dielectric meta- material lens. Appl Phys Lett, 92(13):131904.

[55]Liu LX, Zhang XQ, Kenney M, et al., 2014. Broadband metasurfaces with simultaneous control of phase and amplitude. Adv Mater, 26(29):5031-5036.

[56]Liu R, Ji C, Mock JJ, et al., 2009. Broadband ground-plane cloak. Science, 323(5912):366-369.

[57]Liu RP, Cui TJ, Huang D, et al., 2007. Description and explanation of electromagnetic behaviors in artificial metamaterials based on effective medium theory. Phys Rev E, 76(2):026606.

[58]Liu S, Chen HB, Cui TJ, 2015. A broadband terahertz absorber using multi-layer stacked bars. Appl Phys Lett, 106(15): 151601.

[59]Liu S, Cui TJ, Xu Q, et al., 2016a. Anisotropic coding meta- materials and their powerful manipulation of differently polarized terahertz waves. Light Sci Appl, 5(5):e16076.

[60]Liu S, Cui TJ, Zhang L, et al., 2016b. Convolution operations on coding metasurface to reach flexible and continuous controls of terahertz beams. Adv Sci, 3(10):1600156.

[61]Liu S, Zhang L, Yang QL, et al., 2016c. Frequency‐dependent dual‐functional coding metasurfaces at terahertz frequencies. Adv Opt Mater, 4(12):1965-1973.

[62]Liu S, Zhang HC, Zhang L, et al., 2017. Full-state controls of terahertz waves using tensor coding metasurfaces. ACS Appl Mater Interf, 9(25):21503-21514.

[63]Liu S, Cui TJ, Noor A, et al., 2018. Negative reflection and negative surface wave conversion from obliquely incident electromagnetic waves. Light Sci Appl, 7(5):18008.

[64]Liu XY, Feng YJ, Zhu B, et al., 2016. Backward spoof surface wave in plasmonic metamaterial of ultrathin metallic structure. Sci Rep, 6:20448.

[65]Ma HF, Cui TJ, 2010a. Three-dimensional broadband ground- plane cloak made of metamaterials. Nat Commun, 1(1):21.

[66]Ma HF, Cui TJ, 2010b. Three-dimensional broadband and broad-angle transformation-optics lens. Nat Commun, 1(1):124.

[67]Ma HF, Shen XP, Cheng Q, et al., 2014. Broadband and high‐efficiency conversion from guided waves to spoof surface plasmon polaritons. Laser Photon Rev, 8(1): 146-151.

[68]Ma Q, Shi CB, Bai GD, et al., 2017. Beam‐editing coding metasurfaces based on polarization bit and orbital‐ angular‐momentum‐mode bit. Adv Opt Mater, 5(23): 1700548.

[69]Markovich DL, Andryieuski A, Zalkovskij M, et al., 2013. Metamaterial polarization converter analysis: limits of performance. Appl Phys B, 112(2):143-152.

[70]Minatti G, Maci S, de Vita P, et al., 2012. A circularly- polarized isoflux antenna based on anisotropic metasurface. IEEE Trans Antenn Propag, 60(11):4998-5009.

[71]Moccia M, Liu S, Wu RY, et al., 2017. Coding metasurfaces for diffuse scattering: scaling laws, bounds, and suboptimal design. Adv Opt Mater, 5(19):1700455.

[72]Moitra P, Yang YM, Anderson Z, et al., 2013. Realization of an all-dielectric zero-index optical metamaterial. Nat Photon, 7(10):791-795.

[73]Narimanov EE, Kildishev AV, 2009. Optical black hole: broadband omnidirectional light absorber. Appl Phys Lett, 95(4):041106.

[74]O’Hara JF, Averitt RD, Taylor AJ, 2005. Prism coupling to terahertz surface plasmon polaritons. Opt Expr, 13(16): 6117-6126.

[75]Padilla WJ, Basov DN, Smith DR, 2006. Negative refractive index metamaterials. Mater Today, 9(7-8):28-35.

[76]Park J, Youn JR, Song YS, 2019. Hydrodynamic metamaterial cloak for drag-free flow. Phys Rev Lett, 123(7):074502.

[77]Pendry JB, 2000. Negative refraction makes a perfect lens. Phys Rev Lett, 85(18):3966-3969.

[78]Pendry JB, Holden AJ, Stewart WJ, et al., 1996. Extremely low frequency plasmons in metallic mesostructures. Phys Rev Lett, 76(25):4773-4776.

[79]Pendry JB, Holden AJ, Robbins DJ, et al., 1999. Magnetism from conductors and enhanced nonlinear phenomena,. IEEE Trans Microw Theory Techn, 47(11):2075-2084.

[80]Pendry JB, Martín-Moreno L, Garcia-Vidal FJ, 2004. Mimicking surface plasmons with structured surfaces. Science, 305(5685):847-848.

[81]Pendry JB, Schurig D, Smith DR, 2006. Controlling electromagnetic fields. Science, 312(5781):1780-1782.

[82]Pfeiffer C, Grbic A, 2013. Metamaterial Huygens’ surfaces: tailoring wave fronts with reflectionless sheets. Phys Rev Lett, 110(19):197401.

[83]Qi MQ, Tang WX, Xu HX, et al., 2013. Tailoring radiation patterns in broadband with controllable aperture field using metamaterials. IEEE Trans Antenn Propag, 61(11):5792-5798.

[84]Ramaccia D, Scattone F, Bilotti F, et al., 2013. Broadband compact horn antennas by using EPS-ENZ metamaterial lens. IEEE Trans Antenn Propag, 61(6):2929-2937.

[85]Schurig D, Mock JJ, Justice BJ, et al., 2006. Metamaterial electromagnetic cloak at microwave frequencies. Science, 314(5801):977-980.

[86]Shalaev MI, Sun JB, Tsukernik A, et al., 2015. High-efficiency all-dielectric metasurfaces for ultracompact beam manipulation in transmission mode. Nano Lett, 15(9):6261- 6266.

[87]Shao LD, Zhu WR, Leonov MY, et al., 2019. Dielectric 2-bit coding metasurface for electromagnetic wave manipulation. J Appl Phys, 125(20):203101.

[88]Shelby RA, Smith DR, Schultz S, 2001. Experimental verification of a negative index of refraction. Science, 292(5514):77-79.

[89]Shen XP, Cui TJ, 2013. Planar plasmonic metamaterial on a thin film with nearly zero thickness. Appl Phys Lett, 102(21):211909.

[90]Shen XP, Cui TJ, Martin-Cano D, et al., 2013. Conformal surface plasmons propagating on ultrathin and flexible films. Proc Nat Acad Sci USA, 110(1):40-45.

[91]Shen Z, Jin BB, Zhao JM, et al., 2016. Design of transmission- type coding metasurface and its application of beam forming. Appl Phys Lett, 109(12):121103.

[92]Sievenpiper D, Zhang LJ, Broas RFJ, et al., 1999. High- impedance electromagnetic surfaces with a forbidden frequency band. IEEE Trans Microw Theory Techn, 47(11):2059-2074.

[93]Smith DR, Padilla WJ, Vier DC, et al., 2000. Composite medium with simultaneously negative permeability and permittivity. Phys Rev Lett, 84(18):4184-4187.

[94]Smith DR, Pendry JB, Wiltshire MCK, 2004. Metamaterials and negative refractive index. Science, 305(5685): 788-792.

[95]Sun JB, Liu LY, Dong GY, et al., 2011. An extremely broad band metamaterial absorber based on destructive interference. Opt Expr, 19(22):21155-21162.

[96]Sun SL, He Q, Xiao SY, et al., 2012. Gradient-index meta- surfaces as a bridge linking propagating waves and surface waves. Nat Mater, 11(5):426-431.

[97]Tang WX, Zhang HC, Ma HF, et al., 2019. Concept, theory, design, and applications of spoof surface plasmon polaritons at microwave frequencies. Adv Opt Mater, 7(1): 1800421.

[98]Veselago VG, 1967. Electrodynamics of substances with simultaneously negative values of ε and μ. Usp Fiz Nauk, 92:517-526.

[99]Wakatsuchi H, Kim S, Rushton JJ, et al., 2013. Waveform- dependent absorbing metasurfaces. Phys Rev Lett, 111(24):245501.

[100]Wan X, Shen XP, Luo Y, et al., 2014. Planar bifunctional Luneburg‐fisheye lens made of an anisotropic metasurface. Laser Photon Rev, 8(5):757-765.

[101]Wan X, Qi MQ, Chen TY, et al., 2016a. Field-programmable beam reconfiguring based on digitally-controlled coding metasurface. Sci Rep, 6:20663.

[102]Wan X, Jia SL, Cui TJ, et al., 2016b. Independent modulations of the transmission amplitudes and phases by using Huygens metasurfaces. Sci Rep, 6:25639.

[103]Wan X, Zhang Q, Chen TY, et al., 2019. Multichannel direct transmissions of near-field information. Light Sci Appl, 8(1):60.

[104]Wang M, Ma HF, Zhang HC, et al., 2018. Frequency-fixed beam-scanning leaky-wave antenna using electronically controllable corrugated microstrip line. IEEE Trans Antenn Propag, 66(9):4449-4457.

[105]Wang ZX, Zhang HC, Lu J, et al., 2018. Compact filters with adjustable multi-band rejections based on spoof surface plasmon polaritons. J Phys D, 52(2):025107.

[106]Wei ZY, Cao Y, Su XP, et al., 2013. Highly efficient beam steering with a transparent metasurface. Opt Expr, 21(9): 10739-10745.

[107]Wong AMH, Eleftheriades GV, 2018. Perfect anomalous reflection with a bipartite Huygens’ metasurface. Phys Rev X, 8(1):011036.

[108]Wu HT, Liu S, Wan X, et al., 2017. Controlling energy radiations of electromagnetic waves via frequency coding metamaterials. Adv Sci, 4(9):1700098.

[109]Wu PC, Zhu WM, Shen ZX, et al., 2017. Broadband wide‐angle multifunctional polarization converter via liquid‐metal‐based metasurface. Adv Opt Mater, 5(7): 1600938.

[110]Wu RY, Shi CB, Liu S, et al., 2018. Addition theorem for digital coding metamaterials. Adv Opt Mater, 6(5): 1701236.

[111]Wu RY, Zhang L, Bao L, et al., 2019. Digital metasurface with phase code and reflection-transmission amplitude code for flexible full‐space electromagnetic manipulations. Adv Opt Mater, 7(8):1801429.

[112]Xie BY, Tang K, Cheng H, et al., 2017. Coding acoustic metasurfaces. Adv Mater, 29(6):1603507.

[113]Xu HX, Hu GW, Han L, et al., 2019. Chirality‐assisted high‐efficiency metasurfaces with independent control of phase, amplitude, and polarization. Adv Opt Mater, 7(4): 1801479.

[114]Xu J, Li RQ, Wang SY, et al., 2018. Ultra-broadband linear polarization converter based on anisotropic metasurface. Opt Expr, 26(20):26235-26241.

[115]Yi XN, Ling XH, Zhang ZY, et al., 2014. Generation of cylindrical vector vortex beams by two cascaded metasurfaces. Opt Expr, 22(14):17207-17215.

[116]Yin JY, Ren J, Zhang Q, et al., 2016. Frequency-controlled broad-angle beam scanning of patch array fed by spoof surface plasmon polaritons. IEEE Trans Antenn Propag, 64(12):5181-5189.

[117]Yu NF, Genevet P, Kats MA, et al., 2012. Light propagation with phase discontinuities: generalized laws of reflection and refraction. Science, 334(6504):333-337.

[118]Yu SX, Li L, Shi GM, et al., 2016a. Design, fabrication, and measurement of reflective metasurface for orbital angular momentum vortex wave in radio frequency domain. Appl Phys Lett, 108(12):121903.

[119]Yu SX, Li L, Shi GM, 2016b. Dual-polarization and dual- mode orbital angular momentum radio vortex beam generated by using reflective metasurface. Appl Phys Expr, 9(8):082202.

[120]Yu SX, Li L, Shi GM, et al., 2016c. Generating multiple orbital angular momentum vortex beams using a metasurface in radio frequency domain. Appl Phys Lett, 108(24):241901.

[121]Zhang C, Cao WK, Yang J, et al., 2019. Multiphysical digital coding metamaterials for independent control of broadband electromagnetic and acoustic waves with a large variety of functions. ACS Appl Mater Interf, 11(18): 17050-17055.

[122]Zhang HC, Liu S, Shen XP, et al., 2015a. Broadband amplification of spoof surface plasmon polaritons at microwave frequencies. Laser Photon Rev, 9(1):83-90.

[123]Zhang HC, Fan YF, Guo J, et al., 2015b. Second-harmonic generation of spoof surface plasmon polaritons using nonlinear plasmonic metamaterials. ACS Photon, 3(1): 139-146.

[124]Zhang L, Mei ST, Huang K, et al., 2016. Advances in full control of electromagnetic waves with metasurfaces. Adv Opt Mater, 4(6):818-833.

[125]Zhang L, Liu S, Li LL, et al., 2017. Spin-controlled multiple pencil beams and vortex beams with different polarizations generated by Pancharatnam-Berry coding metasurfaces. ACS Appl Mater Interf, 9(41):36447-36455.

[126]Zhang L, Chen XQ, Liu S, et al., 2018a. Space-time-coding digital metasurfaces. Nat Commun, 9:4334.

[127]Zhang L, Wu RY, Bai GD, et al., 2018b. Transmission‐ reflection‐integrated multifunctional coding metasurface for full‐space controls of electromagnetic waves. Adv Funct Mater, 28(33):1802205.

[128]Zhang L, Chen XQ, Shao RW, et al., 2019. Breaking reciprocity with space‐time‐coding digital metasurfaces. Adv Mater, 31(41):1904069.

[129]Zhang Q, Zhang HC, Yin JY, et al., 2016. A series of compact rejection filters based on the interaction between spoof SPPs and CSRRs. Sci Rep, 6:28256.

[130]Zhang Q, Wan X, Liu S, et al., 2017. Shaping electromagnetic waves using software-automatically-designed metasurfaces. Sci Rep, 7:3588.

[131]Zhang Q, Liu C, Wan X, et al., 2019. Machine‐learning designs of anisotropic digital coding metasurfaces. Adv Theory Simul, 2(2):1800132.

[132]Zhang XG, Tang WX, Jiang WX, et al., 2018. Light― controllable digital coding metasurfaces. Adv Sci, 5(11): 1870068.

[133]Zhang XR, Tang WX, Zhang HC, et al., 2018. A spoof surface plasmon transmission line loaded with varactors and short-circuit stubs and its application in Wilkinson power dividers. Adv Mater Technol, 3(6):1800046.

[134]Zhao J, Cheng Q, Chen J, et al., 2013. A tunable metamaterial absorber using varactor diodes. New J Phys, 15(4): 043049.

[135]Zhao J, Yang X, Dai JY, et al., 2018. Programmable time- domain digital-coding metasurface for non-linear harmonic manipulation and new wireless communication systems. Nat Sci Rev, 6(2):231-238.

[136]Zheludev NI, Kivshar YS, 2012. From metamaterials to metadevices. Nat Mater, 11(11):917-924.

[137]Zheng QQ, Li YF, Zhang JQ, et al., 2017. Wideband, wide- angle coding phase gradient metasurfaces based on Pancharatnam-Berry phase. Sci Rep, 7:43543.

[138]Zheng QQ, Li YF, Han YJ, et al., 2019. Efficient orbital angular momentum vortex beam generation by generalized coding metasurface. Appl Phys A, 125(2):136.