• Photonics Research
  • Vol. 10, Issue 4, 999 (2022)
Guochao Wei1, Zhenzhen Liu1, Licheng Wang1, Jianyuan Song2, and Jun-Jun Xiao1、*
Author Affiliations
  • 1Shenzhen Engineering Laboratory of Aerospace Detection and Imaging, College of Electronic and Information Engineering, Harbin Institute of Technology (Shenzhen), Shenzhen 518055, China
  • 2Shenzhen Suntak Multilayer PCB Co., Ltd., Shenzhen 518115, China
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    DOI: 10.1364/PRJ.453803 Cite this Article Set citation alerts
    Guochao Wei, Zhenzhen Liu, Licheng Wang, Jianyuan Song, Jun-Jun Xiao. Coexisting valley and pseudo-spin topological edge states in photonic topological insulators made of distorted Kekulé lattices[J]. Photonics Research, 2022, 10(4): 999 Copy Citation Text show less

    Abstract

    Photonic topological insulators protected by the lattice spatial symmetry (e.g., inversion and rotation symmetry) mainly support single type edge state, interpreted by either valley or pseudo-spin. Here, we demonstrate theoretically, numerically, and experimentally that a type of judiciously designed two-dimensional Kekulé photonic crystal with time reversal symmetry can possess topological valley and pseudo-spin edge states in different frequency bands. Topologically robust transportation of both the valley and pseudo-spin edge states was confirmed by measuring the transmission of straight and z-shaped interface supported edge mode and comparing with bulk modes in the microwave frequency regime. In addition, we show that due to the distinct topological origins, valley and pseudo-spin edge states can be distinguished by examining their end-scattering into the free space. Our system provides an alternative way in manipulating electromagnetic waves with additional degree-of-freedom, which has potential applications for robust and high-capacity waveguiding and multi-mode dividing.
    H=(0t20t3ei(kx2+3ky2)0t1t20t10t3eikx00t10t20t3ei(kx2+3ky2)t3ei(kx2+3ky2)0t20t100t3eikx0t10t2t10t3ei(kx23ky2)0t20),(A1)

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    Ω(k)=ln(uk1|uk2uk2|uk3uk4|uk3uk1|uk4),(A2)

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    Cv=HBZΩ(k)dS,(A3)

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    Heff=(H+(k)00H(k)).(A4)

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    H+(k)=(0.920.16(kx2+ky2)(0.38+0.32i)(kx+iky)(0.380.32i)(kxiky)0.92+0.16(kx2+ky2)),(A5)

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    H(k)=(0.920.16(kx2+ky2)(0.38+0.32i)(kxiky)(0.380.32i)(kx+iky)0.92+0.16(kx2+ky2)).(A6)

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    H+(k)=H(k)=(0.920.16(kx2+ky2)0.77+0.19(kx2+ky2)0.77+0.19(kx2+ky2)0.92+0.16(kx2+ky2)),(A7)

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    U=(0100100000010010)(B1)

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    Guochao Wei, Zhenzhen Liu, Licheng Wang, Jianyuan Song, Jun-Jun Xiao. Coexisting valley and pseudo-spin topological edge states in photonic topological insulators made of distorted Kekulé lattices[J]. Photonics Research, 2022, 10(4): 999
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