Efficient coupling of single photons to ridge-waveguide photonic integrated circuits

We demonstrate the efficient coupling of single photons emitted by single quantum dots (QDs) in a photonic crystal cavity (PhCC) to a ridge waveguide (RWG). Using a single-step lithographic process with an optimized tapering, up to 70% coupling efficiency between the photonic crystal waveguide and the RWG was achieved. The emission enhancement of single QDs inside an in-line PhCC coupled via the RWG to a single-mode fiber was observed. Single-photon funneling rates around 3.5¿MHz from a single QD into the RWG were obtained. This result is a step toward the realization of a fully functional quantum photonic integrated circuit.