Bichromatic photonic crystal structures are based on the coexistence of two different periodicities in the dielectric constant profile. They are realized starting from a photonic crystal waveguide and modifying the lattice constant only in the waveguide region. In this work, we numerically investigate the spectral and topological properties of bichromatic structures. Our calculations demonstrate that they provide a photonic analog of the integer quantum Hall state, a well-known example of a topological insulator. The nontrivial topology of the bandstructure is illustrated by the formation of strongly localized, topologically protected boundary modes when finite-sized bichromatic structures are embedded in a larger photonic crystal.

中文翻译：

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双色光子晶体中的拓扑边缘态

双色光子晶体结构基于介电常数分布中两个不同周期性的共存。它们是从光子晶体波导开始并且仅在波导区域中修改晶格常数而实现的。在这项工作中，我们数值研究双色结构的光谱和拓扑特性。我们的计算表明，它们提供了整数量子霍尔态的光子类似物，这是拓扑绝缘体的一个著名示例。当有限大小的双色结构嵌入较大的光子晶体中时，通过形成强局部化，拓扑受保护的边界模，可以说明能带结构的非平凡拓扑。