We demonstrate the fabrication of highly efficient sources of entangled photon pairs by inserting a semiconductor
quantum dot in an optical cavity. Two electron-hole pairs trapped in a quantum dot (QD) radiatively recombine emitting
a cascade of two polarization entangled photons. To extract both photons, we use a photonic molecule consisting of two
identical micropillars, one empty, the other embedding a chosen QD. By adjusting the diameter of the pillars and their
relative distance, we ensure that both optical transitions of the QD are simultaneously resonant to cavity modes. The
emitted photon pairs are efficiently extracted thanks to Purcell effect. Doing so, we obtain the brightest sources of
entangled photon pairs to date. We further show that the implementation of Purcell effect allows increasing the fidelity
of the two photon state by reducing spin induced phase shift during the radiative cascade.
Microphotoluminescence experiment has been performed on InAsP/InP epitaxial quantum dots,
emitting in the telecommunication wavelength range. The exciton emission from a single quantum
dot has been detected via the excitation power dependence of the microphotoluminescence spectra.
Two photon entanglement schemes are proposed in order to produce entangled photons out of the
excitonic and bexcitonic transitions in such dot. Both schemes require the implementation of Purcell
effect, in order to collect efficiently the emitted photons and to restore entanglement.
Single photon sources are of extreme interest for future quantum communications networks. Several realizations of such sources where proposed but none of them corresponds to the needs of a quantum network, in terms of emission wavelength, repetition rate or quantum state purity. Using self organized InAs/InP quantum dots, it is
possible to tune the emission wavelength up to 1.55 μm. Lifetime measurements confirm the high optical quality of these dots opening the possibility to engineer sources operate above 77K. With this material combination it is also possible to localized the growth of a single quantum dot, that can be to deterministically coupled to a
photonic crystal cavity.
Optical microcavities offer the ability to create extremely low-threshold lasers with high modulation bandwidth. In such microcavity devices, the fraction β of spontaneous emission into the lasing mode can become close to one and the step-like "threshold" gradually disappears. To implement such high-β devices, one can exploit Cavity Quantum ElectroDynamics effects, more precisely spontaneous emission enhancement. The concomitant effect of spontaneous emission acceleration is the preferential funnelling of spontaneous emission into the cavity mode. In our work, the cavity is a double- heterostructure cavity etched on a suspended membrane and contains InAs quantum dots. Lasing is achieved with β-factors higher than 0.44 and is sustained by less than 10 quantum dots.