Topological physics exploits concepts from geometry and topology to implement systems capable of guiding waves in an unprecedented fashion. These ideas have led to the development of photonic topological insulators, which are optical systems whose eigenspectral topology allows the creation of light states that propagate along the edge of the system without any coupling into the bulk or backscattering even in the presence of disorder. Indeed, topological protection is a fully coherent effect, and it is not clear to what extent topological effects endure when the wavefronts become partially coherent. Here, we study the interplay of topological protection and the degree of spatial coherence of classical light propagating in disordered photonic topological insulators. Our results reveal the existence of a well-defined spectral window in which partially coherent light is topologically protected. This opens up the design space to a wider selection of light sources, possibly yielding smaller, cheaper, and more robust devices based on the topological transport of light.

中文翻译：

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部分相干光的拓扑保护

拓扑物理学利用几何和拓扑的概念来实现能够以前所未有的方式引导波的系统。这些想法导致了光子拓扑绝缘体的发展，这是一种光学系统，其特征光谱拓扑允许创建沿系统边缘传播的光态，即使在存在无序的情况下也不会耦合到体中或反向散射。事实上，拓扑保护是一种完全相干的效应，当波阵面变为部分相干时，拓扑效应能持续到何种程度尚不清楚。在这里，我们研究了拓扑保护的相互作用和经典光在无序光子拓扑绝缘体中传播的空间相干程度。我们的结果揭示了一个定义明确的光谱窗口的存在，其中部分相干光受到拓扑保护。这为更广泛的光源选择打开了设计空间，可能会产生基于光拓扑传输的更小、更便宜和更强大的设备。