Gauge-induced Floquet topological states in photonic waveguides

TL;DR

This paper demonstrates the discovery and experimental verification of gauge-induced Floquet topological states at interfaces in photonic waveguides, enabling robust one-way light propagation through Floquet engineering.

Contribution

It introduces a novel type of topological interface state arising from gauge shifts in Floquet photonic lattices, with experimental validation in silicon waveguides.

Findings

Observation of Floquet { extpi} modes at interfaces

Robust one-way propagation of interface modes

Experimental demonstration with broad bandwidth and high tolerance

Abstract

Tremendous efforts have been devoted to the search for exotic topological states, which usually exist at an interface between lattices with differing topological invariants according to the bulk-edge correspondence. Here, we show a new finding of topological states localized at the interface between two gauge-shifted Floquet photonic lattices, despite the same topological order across the entire structure. The quasienergy band structures reveal that these new interface modes belong to the Floquet {\pi} modes, which are further found to enable a robust one-way propagation thanks to the flexible control of the Floquet gauge. The intriguing propagations of these {\pi}-interface modes are experimentally verified in a silicon waveguides platform at near-infrared wavelengths, which show both broad working bandwidth and high tolerance to the structural fluctuations. Our approach provides a new route for light manipulations with robust behaviours in Floquet engineering and beyond.