Evaluation of oscillator strength in colloidal CdSe/CdS dots‐in‐rods

The oscillator strength in CdSe/CdS colloidal dot-in-rods is evaluated and assessed to be of ∼1.5. On the basis of this finding, the possibility to reach the strong coupling regime with photonic crystals nanocavities is discussed. In spite that carefully choosing the cavity parameters the strong coupling regime could be analytically achieved at room temperature, theoretical considerations show that the typical Rabi doublet cannot be resolved. The work draws also a viable strategy toward the observation of the strong coupling at cryogenic temperatures. (© 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim

Polarized single photon emission for quantum cryptography based on colloidal nanocrystals

In this paper, the evidence of a polarized and room temperature single photon emission from wet-chemically synthesized colloidal dot-in-a-rod is reported. The time and polarization resolved measurements clearly indicate a high degree of linear polarization and a lifetime of ∼11 ns. We report also about a viable strategy to develop single photon sources with polarization control for quantum cryptography

Room temperature-dipolelike single photon source with a colloidal dot-in-rod

We propose colloidal CdSe/CdS dots in rods as nonclassical sources for quantum information technology. Such nanoemitters show specific properties such as strongly polarized emission of on-demand single photons at room temperature, dipolelike behavior and mono-exponential recombination rates, making us envision their suitability as sources of single photons with well defined quantum states in quantum cryptography based devices

Крещение Крыма

Цель статьи - определить место и значение фестивной культуры в условиях социальных трансформаций

Room temperature single-photon sources based on single colloidal nanocrystals in microcavities

Abstract Direct lithography of resist blends, embedding semiconductor colloidal nanocrystals (NCs) is an innovative way to achieve nanopositioning of NCs in quantum-confined optical resonators. In this work, we show a new appealing approach for the fabrication of single-photon sources operating at room temperature by localizing semiconductor colloidal NCs into vertical planar microcavities with lithographic techniques

Contrôle des propriétés quantiques de fluorescence des nanocristaux semi-conducteurs

This thesis focuses on the characterization of nanocrystals whose structure allows to drastically reduce their blinking. The main property of these CdSe nanocrystals is that they are covered by a thick shell of CdS which preserves them from interactions with the surroundings. The realization of a very thick shell is at the origin of the suppression of the long low emitting periods. In addition, we found that if the hole is still blocked into the core of the nanocrystal, the electron is delocalized into the whole structure. This effect causes a reduction of the efficiency of Auger processes. At low pumping rates, this implies that the nanocrystals do not any more exhibit real off periods. This result, combined with measurements of lifetime corresponding to periods of extinction and emission, enabled us to calculate recombination rates of the various processes involved in a low excited nanocristal, whether it is neutral or ionized. At stronger pumping rates, we show the possibility to observe radiative cascades due to multiexcitonic recombinations. The last part of the thesis concerns preliminary results we obtained controlling the emission of nanocrystals by coupling it with a Bragg mirrors photonic cavity. We observed the emission of single photons and we demonstrated the effect of the cavity on the radiative lifetime of individual nanocrystals.Cette thèse a porté principalement sur la caractérisation de nanocristaux dont la structure permet de réduire de façon drastique leur scintillement. La caractéristique essentielle de ces nanocristaux de CdSe est qu'ils sont entourés d'une coquille épitaxiée très épaisse de CdS qui les préserve d'interactions trop importantes avec l'extérieur. La réalisation d'une coquille très épaisse permet de supprimer les longues périodes d'extinction. De plus, on a pu vérifier que si le trou reste localisé dans le coeur du nanocristal, l'électron est délocalisé dans l'ensemble de la structure. Cet effet de délocalisation provoque une réduction de l'efficacité des processus Auger. À bas taux de pompage, cette propriété implique que les nanocristaux ne présentent plus d'états réellement éteints. Ce résultat, associé aux mesures des durées de vie correspondant aux périodes d'extinction et d'émission, nous a permis de calculer les taux de recombinaisons des différents processus en jeu dans un nanocristal faiblement excité, qu'il soit neutre ou ionisé. A plus fort taux de pompage, nous montrons la possibilité d'observer des cascades radiatives consécutives à des recombinaisons d'états multiexcitoniques. La dernière partie a été consacrée à des premiers résultats concernant le contrôle de l'émission de nanocristaux par leur insertion dans des cavités photoniques à miroirs de Bragg. Nous observons l'émission de photons uniques et nous démontrons l'effet de la cavité sur la durée de vie radiative des nanocristaux

Contrôle des propriétés quantiques de fluorescence des nanocristaux semi-conducteurs

PARIS7-Bibliothèque centrale (751132105) / SudocSudocFranceF

Measurement of the working parameters of an air-post vertical-cavity surface-emitting laser

We present a complete experimental evaluation of the effective parameters necessary to describe the dynamical behavior of an air-post vertical-cavity surface-emitting lasers, on the basis of theoretical equations which are also derived in this paper. The experimental investigation is composed of several steps, including power versus current measurement, noise spectrum analysis, linewidth evaluation. The complete set of parameters derived, in particular the linewidth-enhancement factor and the spontaneous emission factor, is particularly important for accurate comparisons of theoretical models on the laser dynamics with experiments