Gauge-induced Floquet topological states in photonic waveguides

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 π 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 π-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.

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References in corpus (5)

• Chiral symmetry and bulk--boundary correspondence in periodically driven one-dimensional systems
• A General Theorem Relating the Bulk Topological Number to Edge States in Two-dimensional Insulators
• Modulated Floquet Topological Insulators
• Nontrivial coupling of light into a defect: the interplay of nonlinearity and topology
• Floquet Majorana zero and $\pi$ modes in planar Josephson junctions