Topological photonic resonator for chiral quantum optics

Topological photonics has enabled unprecedented applications in the field of optics. The resulting topological structures exhibit chiral edge states that are robust to disorder and sharp bends. By coupling these photonic states to quantum emitters, one can generate directional light emission. Even though the previous works have investigated directional light emission in one-dimensional edge states, the extension of this concept to resonator structures has remained elusive. Here we demonstrate chiral light-matter interactions in a topological resonator. We use valley-Hall topological edge states to realize a helical resonator. Such a helical resonator is created at the interface of two distinct topological regions that supports two counter-propagating light modes with opposite polarizations. We show the chiral coupling of the resonator to a quantum emitter. Moreover, we achieve an intensity enhancement of 3.4 due to resonant coupling. Such robust resonators could provide a platform for studying novel many-body dynamics and designing complex nano-photonic circuits.