Nonlinear phenomena are investigated in a topological photonic valley Hall insulator (VHI) using a Kagome system designed to have localized topological boundary state (TBS) at telecommunications wavelengths. Valley Hall topologically protected nonlinear phenomena are demonstrated. Similar transmission properties and parametric wavelength conversion of up to −12 dB are experimentally achieved using sub‐milliwatt average powers in a zigzag interface without back‐scattering, compared with a straight interface. Furthermore, a 7 dB slow light enhancement is observed in the conversion efficiency near the red edge in the transmission band of the boundary state, demonstrating how slow light‐induced backscattering may be circumvented by leveraging the topologically protected boundary state. A Kerr‐induced delocalization of the valley Hall topological state (VHTS) is further experimentally observed, which can be harnessed to control the properties of topological edge states.

中文翻译：

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谷霍尔绝缘体中的拓扑保护参量波长转换

使用 Kagome 系统研究拓扑光子谷霍尔绝缘体 (VHI) 中的非线性现象，该系统设计为在电信波长下具有局部拓扑边界态 (TBS)。论证了 Valley Hall 拓扑保护的非线性现象。与直界面相比，在没有背向散射的锯齿形界面中使用亚毫瓦平均功率，通过实验实现了类似的传输特性和高达 -12 dB 的参量波长转换。此外，在边界态传输带红边附近的转换效率中观察到 7 dB 慢光增强，这证明了如何通过利用拓扑保护的边界态来规避慢光引起的反向散射。通过实验进一步观察到克尔引起的谷霍尔拓扑态（VHTS）的离域，可以利用它来控制拓扑边缘态的性质。