Recently discovered^1,2 valley photonic crystals (VPCs) mimic many of the unusual properties of two-dimensional (2D) gapped valleytronic materials^{3,4,5,6,7,8,9}. Of the utmost interest to optical communications is their ability to support topologically protected chiral edge (kink) states^{3,4,5,6,7,8,9} at the internal domain wall between two VPCs with opposite valley-Chern indices. Here we experimentally demonstrate valley-polarized kink states with polarization multiplexing in VPCs, designed from a spin-compatible four-band model. When the valley pseudospin is conserved, we show that the kink states exhibit nearly perfect out-coupling efficiency into directional beams, through the intersection between the internal domain wall and the external edge separating the VPCs from ambient space. The out-coupling behaviour remains topologically protected even when we break the spin-like polarization degree of freedom (DOF), by introducing an effective spin–orbit coupling in one of the VPC domains. This also constitutes the first realization of spin–valley locking for topological valley transport.

最近发现的^1,2谷光子晶体（VPC）模仿了二维（2D）间隙谷电子材料^{3,4,5,6,7,8,9的}许多不寻常特性。光通信最感兴趣的是它们支持拓扑受保护的手性边缘（扭结）状态^{3、4、5、6、7、8、9的能力。}在两个具有相反的Valley-Chern索引的VPC之间的内部域壁上。在这里，我们通过自旋兼容的四频带模型设计，通过VPC中的极化复用实验演示了谷极化的扭结状态。当谷假自旋被守恒时，我们表明，扭结态通过内部畴壁和将VPC与周围空间隔开的外部边缘之间的交点，表现出接近完美的定向光束输出耦合效率。通过在一个VPC域中引入有效的自旋轨道耦合，即使当我们打破自旋状的极化自由度（DOF）时，外耦合行为仍在拓扑结构上得到保护。这也构成了对旋转谷锁定拓扑山谷运输的第一个实现。