Topological slow light waveguide in photonic valley-locked heterostructures

In this work, a photonic valley-locked heterostructure is proposed, which is composed of a Dirac photonic crystal (DPC) and two valley photonic crystals (VPC), with opposite valley Chern numbers. By modifying the size of rods nearest to the domain walls, the topological valley waveguide state (TVWS) with large group index (n ( g ) = 100) can be found, which is called topological slow-light waveguide mode (TSWM). The simulation results based on finite element method demonstrate that the TSWM supports high energy capacity in the proposed heterostructure waveguide, which is suitable for integrating with the existing waveguides. Besides, TSWM is also valley-locked and immune to backscattering. Our finding paves a way of topological slow light, enrich the research of VPCs, and has new applications in optical communication devices.