Advanced Photonics, Volume. 6, Issue 4, 046005(2024)

Tunable topological polaritons by dispersion tailoring of an active metasurface

Shaojie Wang, Ke Chen*, Shufang Dong, Tian Jiang, Junming Zhao, and Yijun Feng*
Author Affiliations
  • Nanjing University, School of Electronic Science and Engineering, Nanjing, China
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    Figures & Tables(4)
    Electrically reconfigurable topology of polariton dispersions with tunable metasurface. (a) Conceptual schematic of topologically reconfigurable polaritons, where the proposed reconfigurable metasurface allows for surface wavefront control from convex to collimating and eventually to concave and convex, by applying different external bias-voltage. The black arrow represents the excitation source. Bottom-right panels show the schematic of the unit cell. (b), (c) Dispersions of the polaritons along the (b) x and (c) y propagating directions. The right panels show the dispersion diagrams of the polaritons with different loaded capacitance values Cv. (d) Reconfigurable topology of IFCs of the polaritons with loaded capacitances of 0, 0.24, 0.30, and 0.52 pF, respectively. The dashed lines show the IFCs of the first band in the first Brillouin zone at different frequencies. The color maps for the dispersion of polaritons are obtained by simulations in the commercial software Computer Simulation Technology Microwave Studio.
    Simulations and experiments of the topologically active polaritons by the proposed reconfigurable metasurface. (a) Elliptical, flat, hyperbolic, and circular topology of IFC of the polaritons at the observation frequency of 6.1 GHz. (b), (c) Simulated field distributions [real part of the z component of the electric field, Re (Ez)] in the xy plane that is 7 mm above the proposed reconfigurable metasurface (upper panels) and the corresponding dispersions in momentum space [FFT of Re (Ez)] at 6.1 GHz (bottom panels). The observation area covers 54×36 unit cells with a size of 459 mm×306 mm. (d) Photograph of the fabricated sample and experimental setup. (e), (f) Measured field distributions [Re (Ez)] in the xy plane that is 1 mm above the proposed reconfigurable metasurface (upper panels) and the corresponding dispersions in momentum space [FFT of Re (Ez)] at 6.1 GHz (bottom panels). The observation area covers 24×16 unit cells with a size of 204 mm×136 mm. The DC voltages are set as 8 V (Cv=0.25 pF), 6.5 V (Cv=0.29 pF), and 3 V (Cv=0.52 pF) for the measured results of the last three columns. The abbreviation a.u. represents arbitrary units.
    Controllable field canalization and tunable planar focusing based on topological transition of polariton dispersions. (a) Topological transition regions as a function of frequency and loaded capacitance value Cv, which is extracted from the numerical simulations of dispersion diagrams of both the first and the second band in the first Brillouin zone. (b) Measured field distributions [Re (Ez)] in the xy plane that is 1 mm above the reconfigurable metasurface at different frequencies. The observation areas consist of 24×16 unit cells with a size of 204 mm×136 mm. (c) Schematic of the planar focusing as the polaritons propagate from the metasurface into the surrounding air medium. The inset shows the hyperbolic topology of polariton dispersion at 6.1 GHz with the Cv=0.32 pF. The red arrows indicate the propagation directions of the polaritons and the red dot represents the focal point. (d) Measured intensity distributions (|Ez|2) in the xy plane that is 1 mm above the reconfigurable HM at different frequencies. The observation areas have a size of 136 mm×136 mm.
    Reconfigurable integrated polariton circuit. (a) Schematic of the planar reconfigurable polariton circuit composed of two regions (region 1 and region 2) represented by blue and orange blocks, respectively. The loaded capacitances of unit cells are different in region 1 and region 2, leading to different topologies of polariton dispersions. (b)–(d) Simulated field distributions [Re (Ez)] in the xy plane that is 7 mm above the polariton circuit. The right panels show the polariton IFCs in two different regions. The loaded capacitances in region 1 and region 2 are (b) 0.03 and 0.32 pF for realizing the negative refraction, (c) 0.28 and 0.03 pF for realizing the wave splitting, and (d) 0.28 and 0.52 pF for realizing the suppression of polariton propagation. The green dashed circle represents the excitation source. The dotted lines indicate the main propagating directions of the polaritons. The observation areas consist of 64×48 unit cells with a size of 544 mm×408 mm.
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    Shaojie Wang, Ke Chen, Shufang Dong, Tian Jiang, Junming Zhao, Yijun Feng, "Tunable topological polaritons by dispersion tailoring of an active metasurface," Adv. Photon. 6, 046005 (2024)

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    Paper Information

    Category: Research Articles

    Received: May. 4, 2024

    Accepted: Jul. 17, 2024

    Posted: Jul. 17, 2024

    Published Online: Aug. 21, 2024

    The Author Email: Chen Ke (ke.chen@nju.edu.cn), Feng Yijun (yjfeng@nju.edu.cn)

    DOI:10.1117/1.AP.6.4.046005

    CSTR:32187.14.1.AP.6.4.046005

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