  Unidirectional photonic edge states arise at the interface between two
topologically-distinct photonic crystals. Here, we demonstrate a micron-scale
GaAs photonic ring resonator, created using a spin Hall-type topological
photonic crystal waveguide. Embedded InGaAs quantum dots are used to probe the
mode structure of the device. We map the spatial profile of the resonator
modes, and demonstrate control of the mode confinement through tuning of the
photonic crystal lattice parameters. The intrinsic chirality of the edge states
makes them of interest for applications in integrated quantum photonics, and
the resonator represents an important building block towards the development of
such devices with embedded quantum emitters.
