We report the experimental observation of the periodic switching of topological edge states between two dimerized fs-laser written waveguide arrays. Switching occurs due to the overlap of the modal fields of the edge states from topological forbidden gap, when they are simultaneously present in two arrays brought into close proximity. We found that the phenomenon occurs for both strongly and weakly localized edge states and that switching rate increases with decreasing spacing between the topological arrays. When topological arrays are brought in contact with nontopological ones, switching in topological gap does not occur, while one observes either the formation of nearly stationary topological interface mode or strongly asymmetric diffraction into the nontopological array depending on the position of the initial excitation. Switching between topological arrays can be controlled and even completely arrested by increasing the peak power of the input signal, as we observed with different array spacings.

中文翻译：

---

观察拓扑边缘状态的非线性控制切换

我们报告了两个二聚飞秒激光写入波导阵列之间拓扑边缘状态的周期性切换的实验观察。切换是由于拓扑禁隙的边缘状态的模态场的重叠而发生的，当它们同时存在于两个靠得很近的阵列中时。我们发现这种现象发生在强局部化边缘状态和弱局部化边缘状态，并且切换率随着拓扑阵列之间的间距减小而增加。当拓扑阵列与非拓扑阵列接触时，不会发生拓扑间隙的切换，而根据初始激发的位置，观察到几乎静止的拓扑界面模式或强不对称衍射进入非拓扑阵列。