Higher-order topological photonic crystals (TPCs) have attracted much attention in the past several years since they do not obey the conventional bulk-boundary correspondence in topological insulating phases. This characteristic offers a new dimension with which to trap and manipulate the flow of light. In this work, 2D higher-order TPCs for engineering optical second harmonic generation (SHG) are designed. In the TPCs, a topological corner-state is achieved and it is demonstrated that the high localization of photons at the corner-state can significantly promote optical SHG. In addition, topological edge-states are obtained by breaking the Dirac degeneracy point near the SHG frequency. They are also topologically protected and immune to bending resistance. Therefore, the enhanced SHG signal from the corner-state can be manipulated precisely for transmitting through the designed interface with relatively low loss due to the topological-protection edge waves. This design strategy combines the advantages of corner-state and edge-state in higher-order TPCs, demonstrating potential applications of topological photonic devices, such as optical communication and optical computing technologies.

中文翻译：

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操纵高阶拓扑光子晶体中的二次谐波产生

高阶拓扑光子晶体 (TPC) 在过去几年中引起了很多关注，因为它们在拓扑绝缘相中不遵守传统的体边界对应关系。这一特性提供了一个新的维度，可以用来捕捉和操纵光流。在这项工作中，设计了用于工程光学二次谐波生成 (SHG) 的二维高阶 TPC。在 TPC 中，实现了拓扑角态，并且证明了角态处光子的高度定位可以显着促进光学 SHG。此外，拓扑边缘状态是通过打破 SHG 频率附近的狄拉克简并点获得的。它们还受到拓扑保护并且不受弯曲阻力的影响。所以，由于拓扑保护边缘波，来自角态的增强的 SHG 信号可以被精确地操纵以通过设计的界面以相对较低的损耗传输。这种设计策略结合了高阶 TPC 中角态和边缘态的优势，展示了拓扑光子器件的潜在应用，如光通信和光计算技术。