Generation of visible single photons on demand using InP and CdSe quantum dots

Photoluminescence (PL) of both InP and CdSe quantum dots is studied with the aim of generating photonic quantum states on demand. The setup is a scanning confocal microscope with a high numerical aperture objective. The samples are mounted in a liquid helium flow cryostat, where the temperature can be controlled between 3.6 K and room temperature. Excitation is done using either cw or femtosecond pulsed laser light. The PL light can be either sent into a spectrometer or onto two single photo detectors, forming a Hanbury Brown-Twiss arrangement. Time correlation measurements are presented under continuous and pulsed excitation, showing a photon antibunching. For the pulsed case this amounts to single photon generation on demand, where each laser pulse, that creates an excitation inside the quantum dot, produces a single photon. Experiments done on both the excitonic and the biexcitonic transitions and measurements of the spectra and lifetime complement the characterization of the emission process.