On-chip topological nanophotonic devices

On-chip topological nanophotonic devices, which take photons as information carriers with topological protection during light propagation, have great application potential in the next generation photonic chips. The topological photonic states enable the nanophotonic devices to be robust and stable, immune to scattering even with imperfect structures. The development, opportunities and challenges of the on-chip topological nanophotonic devices have attracted great attention of scholars, and desired to be known. In this review, topological devices were introduced in the order of functionalities on an integrated photonic chip, i.e. topological light source, topological light waveguiding, topological light division and selection, topological light manipulation and topological light detecting. Finally, we gave outlooks for predicting and promoting the performances of on-chip topological nanophotonic devices from the angles of non-Hermitian systems, non-Abelian topology, metasurfaces, intelligent algorithms and multiple functional topological nanophotonic integration. This review provides rich knowledge about on-chip topological nanophotonic devices. The insights in this paper will spark inspiration and inspire new thinking for the realization of topological photonic chips.