Three-dimensional photonic topological insulator induced by lattice dislocations

TL;DR

This paper demonstrates a 3D photonic topological insulator with protected edge states enabled by lattice dislocations, using synthetic dimensions in a 2D waveguide array, advancing topological photonics.

Contribution

It introduces a novel method to realize 3D photonic topological insulators via synthetic dimensions and lattice dislocations, which was previously unachieved.

Findings

Successful creation of 3D topological edge states in photonics

Edge states propagate along three-dimensional trajectories

Topological protection similar to strong photonic topological insulators

Abstract

The hallmark of topological insulators is the scatter-free propagation of waves in topologically protected edge channels. This transport is strictly chiral on the outer edge of the medium, and therefore capable of bypassing sharp corners and imperfections, even in the presence of substantial disorder. In photonics, two-dimensional topological edge states have been demonstrated on several different platforms, and are emerging as a promising tool for robust lasers, quantum devices, and other applications. However, three-dimensional photonic topological insulators, specifically those supporting topologically protected edge states in all 3D, have thus far remained out of experimental reach. Here, we demonstrate a three-dimensional photonic topological insulator with protected topological edge states. The topological protection is enabled by a screw dislocation. For this purpose, we utilize the concept of synthetic dimensions in a 2D photonic waveguide array by introducing an additional modal dimension to transform the system into a 3D photonic topological insulator. The lattice dislocation endows the system with edge states propagating along three-dimensional trajectories, with topological protection akin to strong photonic topological insulators. Our work paves the way for utilizing three-dimensional topology in photonic science and technology.