Dual-band topological large-area waveguide transport in photonic heterostructures

Recent advances in all-dielectric topological photonics offer unprecedented opportunities for achieving robust waveguides. However, most topological waveguides are localized at small areas around the interfaces and usually operate in a single frequency window, leading to the low-throughput energy transmission over a narrow bandwidth. Here we report on the implementation of a dual-band topological large-area waveguide in heterostructures based on valley photonic crystals, in which the bandwidths are effectively widen by exploiting the dual-band topology. Inherited from the valley topology, the topological large-area waveguides exhibit the valley-locking effect at two separate frequency windows and are robust against sharp corners and defects. We also observe intriguing topological refractions of the topological large-area waveguides into the ambient space at zigzag and armchair terminations. Our work highlights both the tunable width and the large bandwidth of topological waveguides, paving the way for topological photonic integrated circuits with high performance and multifunctionality.