• Chinese Optics Letters
  • Vol. 19, Issue 6, 060014 (2021)
Rui Ge, Xiongshuo Yan, Yuping Chen*, and Xianfeng Chen
Author Affiliations
  • State Key Laboratory of Advanced Optical Communication Systems and Networks, School of Physics and Astronomy, Shanghai Jiao Tong University, Shanghai 200240, China
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    DOI: 10.3788/COL202119.060014 Cite this Article
    Rui Ge, Xiongshuo Yan, Yuping Chen, Xianfeng Chen. Broadband and lossless lithium niobate valley photonic crystal waveguide [Invited][J]. Chinese Optics Letters, 2021, 19(6): 060014 Copy Citation Text show less

    Abstract

    We investigate the influences of structure parameters and interface shapes on the bandwidth of the edge state of lithium niobate valley photonic crystals. By increasing the size difference of two air holes in the same unit cell, we find that the bandwidth of the lossless nontrivial edge state possesses a peak value of 0.0201(a/λ), which can be used to construct broadband valley photonic crystal waveguides. Mode field distributions verify that the waveguide is robust against sharp bends and exhibits chirality. When the unit cell is arranged in a bearded interface with the top and bottom components showing negative and positive valley Chern numbers, respectively, we find that the lithium niobate valley photonic crystal is more likely to exhibit a lossless edge state, which is difficult to be realized in valley waveguides with low refractive index materials. This work can provide guidance on the design of the high-performance topological waveguide.

    1. Introduction

    The topological valley edge state has recently attracted extensive attention owing to its superior properties like robustness to sharp bends and shows unique Bloch modes with chirality[14]. Researchers have proposed many methods to fulfill valley edge states in photonic crystals, which are mainly based on the same principle where constructing two parts of unit cells that show reversed symmetry with each other allows the top and bottom structures to show opposite valley Chern numbers. Previous works about valley edge states typically focus on their topological protection effect, bandwidth, and loss property[35]. Obtaining a broadband valley waveguide that is simultaneously chiral, lossless, and robust is also a vital goal when designing topological optical waveguides.

    Copy Citation Text
    Rui Ge, Xiongshuo Yan, Yuping Chen, Xianfeng Chen. Broadband and lossless lithium niobate valley photonic crystal waveguide [Invited][J]. Chinese Optics Letters, 2021, 19(6): 060014
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