We demonstrate a single-photon collection efficiency of $(44.3\pm 2.1)\%$ from a quantum dot in a low-Q mode of a photonic-crystal cavity with a single-photon purity of $g^{\left(2\right)}\left(0\right)=(4\pm 5)\%$ recorded above the saturation power. The high efficiency is directly confirmed by detecting up to $962\pm 46$ kilocounts per second on a single-photon detector on another quantum dot coupled to the cavity mode. The high collection efficiency is found to be broadband, as is explained by detailed numerical simulations. Cavity-enhanced efficient excitation of quantum dots is obtained through phonon-mediated excitation and under these conditions, single-photon indistinguishability measurements reveal long coherence times reaching $0.77\pm 0.19$ ns in a weak-excitation regime. Our work demonstrates that photonic crystals provide a very promising platform for highly integrated generation of coherent single photons including the efficient out-coupling of the photons from the photonic chip.

• Received 27 February 2014
• Revised 4 September 2014

DOI:https://doi.org/10.1103/PhysRevB.90.155303