Topological photonic integrated circuits based on valley kink states

TL;DR

This paper experimentally demonstrates topologically protected valley kink states in integrated photonic circuits, enabling robust waveguiding, routing, and resonating of valley-polarized photons with potential applications in optical communication and quantum photonics.

Contribution

It introduces the experimental realization of valley kink states in photonic circuits and explores their applications in robust photonic devices and topological photonics research.

Findings

Backscattering-free waveguiding at sharp bends

High-Q topological photonic crystal cavities

Counterintuitive optical routing based on valley pseudospin

Abstract

Valley pseudospin, a new degree of freedom in photonic lattices, provides an intriguing way to manipulate photons and enhance the robustness of optical networks. Here we experimentally demonstrated topological waveguiding, refracting, resonating, and routing of valley-polarized photons in integrated circuits. Specifically, we show that at the domain wall between photonic crystals of different topological valley phases, there exists a topologically protected valley kink state that is backscattering-free at sharp bends and terminals. We further harnessed these valley kink states for constructing high-Q topological photonic crystal cavities with tortuously shaped cavity geometries. We also demonstrated a novel optical routing scheme at an intersection of multiple valley kink states, where light splits counterintuitively due to the valley pseudospin of photons. These results will not only lead to robust optical communication and signal processing, but also open the door for fundamental research of topological photonics in areas such as lasing, quantum photon-pair generation, and optomechanics.