ACS Photon. http://doi.org/b8j6 (2017)

A bright and efficient integrated single-photon source has been made by combining a single InGaAs quantum dot with an optical element made by 3D printing technology. Scientists from Berlin and Stuttgart used electron-beam lithography to integrate the quantum dot with a GaAs microlens that sits on top of a distributed Bragg reflector. A multi-lens micro-objective was then fabricated by 3D femtosecond direct laser writing and precisely aligned to the microlens in order to efficiently extract the emitted photons. The resulting light source operates with a photon extraction efficiency of ∼40%. The team says that excellent single-photon purity is obtained with a g(2) factor of <0.02, which indicates strongly suppressed multiphoton emission. The approach enables the excitation power for driving the emitter to be decreased by an order of magnitude. Future plans are to create a plug-and-play fibre-coupled single-photon source using the approach.