Resonance fluorescence revival in a voltage-controlled semiconductor quantum dot

We demonstrate systematic resonance fluorescence recovery with near-unity emission efficiency in single quantum dots embedded in a charge-tunable device in a wave-guiding geometry. The quantum dot charge state is controlled by a gate voltage, through carrier tunneling from a close-lying Fermi sea, stabilizing the resonantly photocreated electron-hole pair. The electric field cancels out the charging/discharging mechanisms from nearby traps toward the quantum dots, responsible for the usually observed inhibition of the resonant fluorescence. Fourier transform spectroscopy as a function of the applied voltage shows a strong increase of the coherence time though not reaching the radiative limit. These charge controlled quantum dots act as quasi-perfect deterministic single-photon emitters, with one laser pulse converted into one emitted single photon

Room temperature spontaneous emission enhancement from quantum dots in photonic crystal slab cavities in the telecommunications C-band

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 44x10^3 with an ultra-low modal volume of the order of 1.2 lambda/n)^3, inducing an enhancement of the spontaneous emission rate of up a factor of 2.8 at 300 K

Single InAsP/InP quantum dots as telecommunications-band photon sources

The optical properties of single InAsP/InP quantum dots are investigated by spectrally-resolved and time-resolved photoluminescence measurements as a function of excitation power. In the short-wavelength region (below 1.45 $\mu$m), the spectra display sharp distinct peaks resulting from the discrete electron-hole states in the dots, while in the long-wavelength range (above 1.45 $\mu$m), these sharp peaks lie on a broad spectral background. In both regions, cascade emission observed by time-resolved photoluminescence confirms that the quantum dots possess discrete exciton and multi-exciton states. Single photon emission is reported for the dots emitting at 1.3 $\mu$m through anti-bunching measurements

Étude des propriétés optiques et dynamiques des boîtes quantiques InAsP/InP(001); Application à la réalisation de sources de photons uniques et lasers à cristaux photoniques émettant à 1.5 µm

The last century saw the advent of quantum mechanics, information processing and integrated optics. These fields lead to the integrated optics for quantum communication. One of the challenges is the development of single photon sources and compact lasers operating at telecommunication wavelength, for quantum cryptography and quantum information applications. In this work, we present an optical study of InAsP/InP [001] quantum dots, obtained by MetalOrganic Vapour Phase Epitaxy (MOVPE). It has been demonstrated, through spectral measurements and time-resolved photoluminescence experiments, that these quantum dots present the characteristics necessary for the applications mentioned. Specifically, we have performed measurments with single dots and we clearly observed a photon antibunching. This quantum behaviour, validates the feasibility of a single photons source at telecommunication wavelength. In parallel, studies on photonic crystal lasers, with low modal volume and high quality factor, using the same quantum dots at room temperature, showed original properties, specially near the threshold region of the lasing transition. The difference between conventionnal lasers and our structures is explained with the high spontaneous emission coupling through the cavity mode.Le siècle dernier a vu l'accomplissement de la mécanique quantique, du traitement de l'information et de l'optique intégrée. Aujourd'hui, ces trois domaines se rencontrent pour donner naissance à l'optique intégrée pour les communications quantiques. Un des enjeux aujourd'hui dans ce domaine est le développement de sources de photons uniques et de lasers compacts aux longueurs d'onde des télécommunications. Les émetteurs étudiés dans ce travail de thèse sont des boîtes quantiques InAsP/InP [001] obtenues par Epitaxie en Phase Vapeur aux OrganoMétalliques (EPVOM). Il a été démontré, par l'intermédiaire de mesures spectrales et des mesures de durée de vie, que ces émetteurs présentent les caractéristiques nécessaires en vue des applications visées. Plus particulièrement, la mise en évidence expérimentale d'un dégroupement de photons, à partir d'une boîte unique, valide la possibilité de réaliser une source de photons uniques. En parallèle, des études sur les lasers à cristaux photoniques de faible volume modal et fort facteur de qualité, utilisant les mêmes boîtes quantiques à température ambiante, ont montré des propriétés originales, particulièrement sur la physique au niveau du seuil laser. La différence de comportement au niveau du seuil, par rapport aux lasers conventionnels, s'explique dans nos structures par le fort taux de couplage de l'émission spontanée dans le mode laser

Resonance fluorescence of a single semiconductor quantum dot : the impact of a fluctuating electrostatic environment

International audienceSemiconductor quantum dots are very efficient sources of single and highly indistinguishable photons. These properties rely on the possibility to coherently control the system at the single spin level. At this ultimate level of control, the quantum dot becomes a very sensitive probe of its solid-state environment and any interaction turns into a dephasing process that alters its coherence properties. In this topical review, we give an overview of the issue of charge noise which remains one of the main dephasing mechanisms to overcome. This phenomenon which strongly depends on sample preparation, originates from a fluctuating electrostatic landscape around the quantum dots and renders a unified description quite awkward. We present the common characteristic features induced by charge noise that have been observed in the resonant fluorescence experiments of single quantum dots and discuss the different approaches that have been proposed in the literature to circumvent this problem

L’établissement rural de la Chapellière à la Chaize-le-Vicomte (Vendée) : une ferme gauloise de la fin du deuxième Âge du Fer (IIe siècle-Ier siècle a.C.)

Realised before the construction of the motorway A87, the excavation of la Chapellière revealed a late La Tène settlement closed by a quadrangular enclosure of 1,5 ha. This rural settlement was divided in two parts by an internal ditch. Beyond dug structures, pits, combustion structures and wells, several buildings were discovered witch could be interpreted as houses or annexes to stock. Several fields and a way give a picture of the country around the site during the Late Iron Age. Because of the short time of occupation, it’s possible to consider the pottery of la Chapellière as a whole characteristic to the end of the II nd century and the beginning of the Ist century B. C. The discover of eight gaulish coins in electrum must be mentioned too.Réalisée préalablement aux travaux de construction de l’autoroute A87, la fouille du site de la Chapellière a révélé une occupation de la fin de La Tène sur une superficie de près de 10 ha. L’établissement rural découvert est délimité par un enclos quadrangulaire de 1,5 ha divisé en deux par un fossé de partition interne. Outre des structures en creux, fosses, structures de combustion et puits, plusieurs ensembles bâtis ont été mis en évidence. Ils peuvent être interprétés, selon le cas, comme des habitations ou des annexes liées aux activités agricoles. Plusieurs parcelles ainsi qu’un chemin donnent une idée du paysage environnant à la fin de l’âge du Fer. La faible durée de l’occupation a permis d’étudier un ensemble céramique homogène représentatif de la fin du IIe siècle et du début du Ier siècle a. C. Il faut aussi signaler la découverte d’un ensemble monétaire composé de huit monnaies en métaux précieux.Maguer Patrick, Arthuis Rémy, Hiernard Jean, Hostein Héléna, Richard J.-M. L’établissement rural de la Chapellière à la Chaize-le-Vicomte (Vendée) : une ferme gauloise de la fin du deuxième Âge du Fer (IIe siècle-Ier siècle a.C.). In: Aquitania : une revue inter-régionale d'archéologie, tome 21, 2005. pp. 21-72

Ultra-stable microwave cryogenic oscillator operated with a Gifford-McMahon cryocooler

International audienceWe demonstrate for the first time an ultra-stable microwave cryogenic oscillator operated with a Gifford-McMahon (GM) cryocooler. Despite the high level of vibration generated by the GM, we show that an optimised design, with simple passive solutions, enables a sufficient mechanical decoupling to achieve a state-of-the-art frequency stability. The implemented 10 GHz cryogenic oscillator features a fractional frequency stability (ADEV, Allan deviation) σy(τ ) < 3×10−15 for 1 s ≤ τ ≤ 104 s