High-Q tunable orbital angular momentum radiation

Lasers and light emitters typically do not radiate fields with orbital angular momentum (OAM). So far, the generation of single photons carrying OAM mainly relies on nonlinear processes in bulk crystals, which limits the scalability and efficiency of the source. To facilitate the realization of highly efficient OAM single-photon sources, we demonstrate a microresonator vortex emitter producing high-<i>Q</i> OAM vortex beams with the ability to precisely define the topological charge of the OAM mode. The phenomenon relies on the application of periodic perturbations on the nanobars, which generate a series of resonance modes in continuous guided spectra. Future developments of integrated quantum photonic devices with OAM single-photon sources may enable high-dimensional quantum information processing.