Efficient and selective cavity-resonant excitation for single photon generation

We present an efficiently pumped single photon source based on single quantum dots embedded in photonic crystal nanocavities. Resonant excitation of a single quantum dot via a higher order cavity mode is shown to result in a 100 x reduced optical power at the saturation onset of the photoluminescence, compared with excitation at the same frequency, after the cavity mode is shifted. We demonstrate that this excitation scheme leads to selective excitation only of quantum dots that are coupled to the cavity by comparing photoluminescence and auto-correlation spectra for the same excitation wavelength, with and without spectral resonance with the cavity mode. This excitation technique provides cleaner conditions for single photon generation and a method to select a subset of quantum dots that are spatially coupled to the nanocavity mode.