Single photon emission at telecom wavelength is observed in InAsP/InP QDs. These dots will be embedded in a metallic subwavelength plasmonic cavity allowing for broadband Purcell factors allowing the engineering of efficient entangled-photon sources.

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.

Cette these etudie l'ingenierie, a partir de boites quantiques uniques (BQ), de sources deterministes de paires de photons intriques selon deux procedes: l'intrication en polarisation lors de la cascade radiative du bi-exciton, et l'intrication temporelle de deux photons indisscernables. Le degre d'intrication est calcule afin d'evaluer quantitativement l'impact de: la levee de degenerescence de l'exciton (splitting), le renversement de spin, l'interaction de l'exciton avec son environnement. Dans les deux cas l'intrication peut etre restauree en accelerant la duree de vie radiative de l'exciton par effet Purcell. Pour cela, un moyen approprie est une cavite a cristal photonique gravee dans une membrane suspendue (CP2D) contenant la BQ, qui permet aussi une grande efficacite de collection. Les requis technologiques d'alignement de la boite quantique avec la cavite sont aussi etudies. Cependant les effets de cavite sont insuffisants pour corriger le splitting, qui peut etre reduit avec un champ electrique variable vertical. Ceci a ete verifie experimentalement en developpant une technologie pour produire des diodes PIN compatibles avec les CP2D.

We report on the control of the spontaneous emission dynamics from InAsP self-assembled quantum dots emitting in the telecommunications C band and weakly coupled to the mode of a double heterostructure cavity etched on a suspended InP membrane at room temperature. The quality factor of the cavity mode is 44×103 with an ultralow modal volume of the order of 1.2(λ/n)3, inducing an enhancement in the spontaneous emission rate of up a factor of 2.8 at 300 K.

We report on the theoretical investigation of photonic crystal cavities etched on a suspended membrane for the generation of polarization entangled photon pairs using the biexciton cascade in a single quantum dot. The implementation of the spontaneous emission enhancement effect increases the entanglement visibility, while the concomitant preferential funneling of the emission in the cavity mode increases the collection of both entangled photons. We demonstrate and quantify that standard cavity designs present a polarization-dependent emission diagram, detrimental to entanglement. The optimization of H1 cavities allows us to obtain both high collection efficiencies and polarization-independent emission, while keeping the high Purcell factors necessary for high-quality entangled photon sources.

Photonic crystal based nanolasers have sprung a lot of interest in the latest years due to the high optical confinement of the cavity. High quality factor cavities in conjunction with low electromagnetical volumes, allows to implement a significant enhancement of the spontaneous emission dynamics and hence a preferential funnelling of spontaneously emitted photons into the laser mode. Theoretical predictions on such lasers with high spontaneous emission coupling factors beta include a smooth transition from spontaneous to stimulated emission, but also high large signal modulation bandwidth.

We report on a scheme for the creation of time-bin entangled states out of two subsequent single photons. Both photons arrive on the same input port of a beamsplitter and the situation in which the photons leave the beamsplitter on different output ports is post-selected. We derive a full quantum mechanical analysis of such time-bin entanglement for emitters subject to uncorrelated dephasing processes and apply this model to sequential single photons emerging from a single semiconductor quantum dot. Our results indicate that the visibility of entanglement is degraded by decoherence effects in the quantum dot, but can be restored by use of CQED effects, namely the Purcell effect.

We theoretically investigate the joint photodetection probabilities of the biexciton-exciton cascade in single semiconductor quantum dots and analytically derive the density matrix and the Bell's inequalities of the entangled state. Our model includes different mechanisms that may spoil or even destroy entanglement such as dephasing, energy splitting of the relay excitonic states, and incoherent population exchange between these relay levels. We explicitly relate the fidelity of entanglement to the dynamics of these processes and derive a threshold for violation of Bell's inequalities. Applied to standard InAs/GaAs self-assembled quantum dots, our model indicates that spontaneous emission enhancement of the excitonic states by cavity effects increases the fidelity of entanglement to a value allowing for violation of Bell's inequalities.