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

Abstract

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.