  Using the zero-phonon line (ZPL) emission of a single molecule, we realized a
triggered source of near-infra-red (lambda=785 nm) single photons at a high
repetition rate. A Weierstrass solid immersion lens is used to image single
molecules with an optical resolution of 300 nm (~0.4*lambda) and a high
collection efficiency. Because dephasing of the transition dipole due to
phonons vanishes at liquid helium temperatures, our source is attractive for
the efficient generation of single indistinguishable photons.
