Frequency dependent wave routing based on dual-band valley-Hall topological photonic crystal

Abstract

Previous studies on the propagation direction of valley topological edge states mainly focus on the matching between orbital angular momentum of the excitation source and specific pseudo-spin state of valley edge mode at certain frequency that falls in the bandgap of the topologically distinct bulk components. In this work, we propose topological photonic crystals (PCs) hosting two topological protected bandgaps. It is shown that by constructing the interface between different PC structures with distinct topological phase, edge states can be engineered inside these two bandgaps, which provides a convenient way to achieve flexible wave routing. Particularly, we study three types of meta-structures consisting of these PCs in which the valley edge states routing path highly depends on the operating frequency and inputting port of the excitation source. Our study provides an alternative way in designing topological devices such as wave splitters and frequency division devices.