Non‐Blinking Single‐Photon Generation with Anisotropic Colloidal Nanocrystals: Towards Room‐Temperature, Efficient, Colloidal Quantum Sources

Blinking and single-photon emission can be tailored in CdSe/CdS core/shell colloidal dot-in-rods. By increasing the shell thickness it is possible to obtain almost non-blinking nanocrystals, while the shell length can be used to control single-photon emission probability

Investigating the fast spectral diffusion of a quantum emitter in hBN using resonant excitation and photon correlations

The ability to identify and characterize homogeneous and inhomogeneous dephasing processes is crucial in solid-state quantum optics. In particular, spectral diffusion leading to line broadening is difficult to evidence when the associated timescale is shorter than the inverse of the photon detection rate. Here, we show that a combination of resonant laser excitation and second-order photon correlations allows to access such fast dynamics. The resonant laser drive converts spectral diffusion into intensity fluctuations, leaving a signature in the second-order coherence function $g^{(2)}(\tau)$ of the scattered light that can be characterized using two-photon coincidences -- which simultaneously provides the homogeneous dephasing time. We experimentally implement this method to investigate the fast spectral diffusion of a color center generated by an electron beam in the two-dimensional material hexagonal boron nitride. The $g^{(2)}(\tau)$ function of the quantum emitter measured over more than ten orders of magnitude of delay times, at various laser powers, establishes that the color center experiences spectral diffusion at a characteristic timescale of a few tens of microseconds, while emitting Fourier-limited single photons ($T_2/2T_1 \sim 1$) between spectral jumps

Spatially uniform enhancement of single quantum dot emission using plasmonic grating decoupler

International audience1 We demonstrate a spatially uniform enhancement of individual quantum dot (QD) fluorescence emission using plasmonic grating decouplers on thin gold or silver films. Individual QDs are deposited within the grating in a controlled way to investigate the position dependency on both the radiation pattern and emission enhancement. We also describe the optimization of the grating decoupler. We achieve a fluorescence enhancement ~3 times higher than using flat plasmon film, for any QD position in the grating. Future optical quantum devices require the development of photonic sources with control of light down to the single photon limit. Excellent examples of single photon emitters are the colloidal nanocrystal quantum dots (QDs) which are considered as the building blocks for future quantum devices such as quantum qubits and quantum cryptographic devices 1,2. The application area of quantum emitters is wide and these applications require control of their emission such as emission rate, polarization, spectral properties, collection efficiency etc. Integration of single molecule or nanocrystals into plasmonic structures has recently proved to be one of the most promising yet challenging ways to control the emission properties at the single photon level 3,

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

Etude du bruit quantique dans les microlasers semi-conducteurs à cavité verticale (VCSELs) et les lasers à solide Nd:YVO4

We study in detail the quantum noise in a new type of semiconductor lasers, the VCSELs (for Vertical-Cavity Surface-Emitting Lasers). These lasers can operate with various transverse modes with different polarisations above threshold. When only one transverse mode linearly polarised oscillate, we demonstrate experimentally as well as theoretically that one has to take into account the noise of the modes orthogonally polarised under threshold to characterise the intensity noise. When various transverse modes oscillate, they are strongly anticorrelated which gives rise to squeezing for the best samples. If a sample always shows excess noise in free-running operation, the injection locking technique is a way to obtain intensity squeezed beams. Finally, we report our results concerning the transverse spatial structure of the intensity noise. We also study the intensity noise of Nd:YVO4 microlasers. Compared to the theoretical predictions of the standard 2 level laser theory, the experimental results exhibit an excess noise at low frequencies. We demonstrate that this excess noise is due to non linear effects at the relaxation oscillation frequency. These effects are reduced experimentally by two different techniques: an electrooptic feedback loop or the injection locking.Nous étudions en détail le bruit quantique dans les microlasers semi-conducteurs à cavité verticale : les VCSELs, dont l'acronyme anglais signifie Vertical-Cavity Surface-Emitting Lasers. Ces lasers ont la particularité d'émettre des faisceaux avec plusieurs modes transverses de polarisations variées au-dessus du seuil. Lorsqu'un seul mode transverse, polarisé linéairement oscille, nous démontrons théoriquement aussi bien qu'expérimentalement l'importance de l'émission dans la direction de polarisation orthogonale pour la caractérisation du bruit d'intensité. En régime multimode transverse, les anticorrélations très importantes entre les modes permet d'obtenir, pour les meilleurs échantillons, des faisceaux au bruit d'intensité comprimé (jusqu'à 15 % sous la limite quantique standard). Pour les échantillons qui présentent de l'excès de bruit en régime libre, la technique de l'injection optique permet d'obtenir, dans certains cas, de la compression du bruit d'intensité. Enfin, nous présentons nos résultats sur la structure spatiale du bruit d'intensité dans le plan transverse. Nous rapportons aussi dans ce manuscrit l'étude du bruit d'intensité des minilasers Nd :YVO4. Par rapport au modèle standard des lasers à deux niveaux, ces lasers présentent un excès de bruit à basse fréquence. Nous montrons que cet excès de bruit provient d'effets non linéaires dus à l'importance du pic de bruit à la fréquence d'oscillation de relaxation. Expérimentalement, nous mettons en oeuvre deux techniques distinctes pour réduire ces effets : une boucle de rétroaction électrooptique et l'injection optique

ETUDE DU BRUIT QUANTIQUE DANS LES MICROLASERS SEMI-CONDUCTEURS A CAVITE VERTICALE (VCSELS) ET LES LASERS A SOLIDE ND (YVO 4)

PARIS-BIUSJ-Physique recherche (751052113) / SudocCentre Technique Livre Ens. Sup. (774682301) / SudocSudocFranceF

Cohérence temporelle des photons uniques émis par un nanocristal individuel de CdSe/ZnS

PARIS7-Bibliothèque centrale (751132105) / SudocSudocFranceF

Contrôle des propriétés quantiques de fluorescence des nanocristaux semi-conducteurs

PARIS7-Bibliothèque centrale (751132105) / SudocSudocFranceF

Propriétés quantiques de la fluorescence de nanocristaux CdSe/CdS déposés sur des nanostructures métalliques

VERSAILLES-BU Sciences et IUT (786462101) / SudocSudocFranceF