Photonic Topological Insulator Edge Modes Using All-Dielectric Kagome Photonic Crystals

Photonic topological insulators are promising photonic structures which can exhibit unidirectional propagation of edge states insensitive to bendings, fabrication imperfections or temperature variations. Recently, an all-dielectric perturbed honeycomb topological photonic crystal has attracted attention due to its simplicity of fabrication. However, its edge states intrinsically suffer from back-reflection due to the symmetry breaking at the interface. Here, we propose an all-dielectric reciprocal photonic topological insulator based on the geometry of a kagome lattice in which the topological edge modes do not undergo back-reflection for termination along the $\Gamma - K$ direction. In contrast to the perturbed honeycomb, the edge modes in our kagome-based structure are below the light cone leading to improved vertical mode confinement.