Switching on topology Ways to control and design topological features in various systems are being studied intensively because the resulting properties tend to be robust against things such as scattering and defects, endowing the system with topological protection. Maczewsky et al. now look to another regime in optics to show that optical nonlinearity can induce a topological change in the properties of a photonic lattice. At low excitation power, probe light uniformly leaks into the rest of the lattice, an optically trivial phase. Above a threshold power, optical nonlinearity induces a topological change in the properties of the photonic lattice, and probe light is confined to propagate along the edge of the structure. These results illustrate a route to dynamically control the propagation of light. Science, this issue p. 701 Optical nonlinearity induces a transition from trivial to topological propagation of light in a photonic lattice. A hallmark feature of topological insulators is robust edge transport that is impervious to scattering at defects and lattice disorder. We demonstrate a topological system, using a photonic platform, in which the existence of the topological phase is brought about by optical nonlinearity. The lattice structure remains topologically trivial in the linear regime, but as the optical power is increased above a certain power threshold, the system is driven into the topologically nontrivial regime. This transition is marked by the transient emergence of a protected unidirectional transport channel along the edge of the structure. Our work studies topological properties of matter in the nonlinear regime, providing a possible route for the development of compact devices that harness topological features in an on-demand fashion.

中文翻译：

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非线性诱导光子拓扑绝缘体

切换拓扑 正在深入研究各种系统中控制和设计拓扑特征的方法，因为由此产生的特性往往对散射和缺陷等事物具有鲁棒性，从而赋予系统拓扑保护。Maczewsky 等人。现在看看光学中的另一种机制，以表明光学非线性可以引起光子晶格特性的拓扑变化。在低激发功率下，探测光均匀地泄漏到晶格的其余部分，这是一个光学微不足道的阶段。超过阈值功率时，光学非线性会引起光子晶格特性的拓扑变化，并且探测光被限制为沿结构边缘传播。这些结果说明了动态控制光传播的途径。科学，这个问题 p。701 光学非线性导致光子晶格中光从平凡传播到拓扑传播的转变。拓扑绝缘体的一个标志特征是强大的边缘传输，它不受缺陷和晶格无序散射的影响。我们展示了一个使用光子平台的拓扑系统，其中拓扑相位的存在是由光学非线性引起的。晶格结构在线性状态下保持拓扑微不足道，但随着光功率增加到某个功率阈值以上，系统被驱动到拓扑非微不足道的状态。这种转变的特点是沿结构边缘暂时出现了受保护的单向传输通道。我们的工作研究非线性状态下物质的拓扑特性，