Abstract

Propagating topological edge states have been extensively studied in two-dimensional photonic topological insulators (TIs) [1]. Apart from other photonic TIs in higher dimensions, 3D TIs have recently been implemented with microwaves [2] and acoustic waves [3], the latter inducing topology through a dislocation. Here we report the first experimental demonstration of a three-dimensional topological insulator at optical frequencies and observe the propagation dynamics of its unidirectional edge states in two spatial and one modal dimensions [4]. In our system, the introduction of a screw dislocation into a weak 3DTI serves to establish a closed 3-dimensional path that encircles the 3D structure around the outer parameter and loops back along the axis of the dislocation.

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