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Organic–inorganic layered perovskites are currently some of the most promising 2D van der Waals materials. Low crystal quality usually broadens the exciton line width, obscuring the fine structure of the exciton in conventional photoluminescence experiments. Here, we propose a mechanical approach to reducing the effect of spectral diffusion by means of hBN capping on layered perovskites, revealing the exciton fine structure. We used a stochastic model to link the reduction of the spectral line width with the population of charge fluctuation centers present in the organic spacer. van der Waals forces between both lattices cause the partial clamping of the perovskite organic spacer molecules, and hence the amplitude of the overall spectral diffusion effect is reduced. Our work provides a low-cost solution to the problem of accessing important fine-structure excitonic state information, along with an explanation of the important carrier dynamics present in the organic spacer that affect the quality of the optical emission.

The interaction of Ge(Si)/SOI self-assembled nanoislands with modes of photonic crystal slabs (PCS) with a hexagonal lattice is studied in detail. Appropriate selection of the PCS parameters and conditions for collecting the photoluminescence (PL) signal allowed to distinguish the PCS modes of different physical nature, particularly the radiative modes and modes associated to the bound states in the continuum (BIC). It is shown that the radiative modes with relatively low Q-factors could provide a increase greater than an order of magnitude in the integrated PL intensity in the wavelength range of 1.3–1.55 µm compared to the area outside of PCS at room temperature. At the same time, the interaction of Ge(Si) islands emission with the BIC-related modes provides the peak PL intensity increase of more than two orders of magnitude. The experimentally measured Q-factor of the PL line associated with the symmetry-protected BIC mode reaches the value of 2600.

GaInP microdisks contained InP/GaInP quantum dots having lateral size ∼150 nm and 1-5 μm−2 were investigated with help of microphotoluminescence technique. Experiments carried out in confocal, time-resolved and low-temperature modes. Comparison of results allowed to conclude that overlap of quantum dot emission area with whispering gallery mode antinode results in faster luminescence lifetime (Purcell effect). Whispering gallery mode lasing was detected. Obtained threshold power values were following 6 µW (Q=4500, T=8.5 K) and 0.4 µW (Q=7400, T=80 K).

В данной работе исследованы микродисковые резонаторы диаметром 2 мкм с квантовыми точками InP/GaInP. Основным методом исследования является микрофотолюминесцения каждого из двух образцов. Исследование зависимости микрофотолюминесценции двух структур от мощности постоянной оптической накачки показало генерацию для обоих образцов. Переход в режим генерации подтвержден сужением спектральной ширины линии при достижении порога генерации и в послепороговом режиме, а также корреляционными измерениями первого образца, подтверждающими появление когерентного излучения при достижении пороговой мощности накачки. Время-разрешенные спектроскопические исследования показали возможность наблюдения эффекта Парселла на образцах при малой мощности. При анализе экспериментальных данных с помощью скоростных уравнений для микрорезонаторов установлен вид зависимости интенсивности излучения микродисков от мощности накачки. Показано, что использование в качестве активной области лазеров квантовых точек с большим латеральным размером и малой плотности позволяет получить наиболее низкие пороги лазерной генерации., The given work is devoted to the laser generation of microdisk resonators with a diameter of 2 μm with InP/GaInP quantum dots. The main research method is microphotoluminescence of each sample. A study of the dependence of microphotoluminescence of two structures at the constant optical pump power showed lasing for both samples. The transition to the generation mode is confirmed by spectral line width narrowing at the generation threshold and after it. It is shown that the correlation measurements of the first sample confirm the change of photon statistics and appearance of coherent emission after the threshold. Time-resolved spectroscopy studies have shown the possibility of observing the Purcell effect at low power. When analyzing the experimental data using the rate equations for microcavities, the dependence of the luminescence intensity on the pump power is established. It is shown that the use of quantum dots with a large lateral size and low density as the active region for lasers makes it possible to obtain the lowest laser generation thresholds.

Lead-halide perovskite APbX3 (A = Cs or organic cation; X = Cl, Br, I) nanocrystals (NCs) are the subject of intense research due to their exceptional characteristics as both classical and quantum light sources. Many challenges often faced with this material class concern the long-term optical stability, a serious intrinsic issue connected with the labile and polar crystal structure of APbX3 compounds. When conducting spectroscopy at a single particle level, due to the highly enhanced contaminants (e.g., water molecules, oxygen) over the NC ratio, deterioration of NC optical properties occurs within tens of seconds with typically used excitation power densities (1–100 W/cm2) and in ambient conditions. Here, we demonstrate that choosing a suitable polymer matrix is of paramount importance for obtaining stable spectra from a single NC and for suppressing the dynamic photoluminescence blueshift. In particular, polystyrene (PS), the most hydrophobic among four tested polymers, leads to the best optical stability, one to two orders of magnitude higher than that obtained with poly(methyl methacrylate), a common polymeric encapsulant containing polar ester groups. Molecular mechanics simulations based on a force-field approximation corroborate the hypothesis that PS affords for a denser molecular packing at the NC surface. These findings underscore the often-neglected role of the sample preparation methodologies for the assessment of the optical properties of perovskite NCs at a single-particle level and guide the further design of robust single photon sources., Nano Letters, 19 (6), ISSN:1530-6984, ISSN:1530-6992

This PhD addresses the development of high-power laser diodes emitting at 975nm withhigh efficiency and wavelength stabilized using a Bragg grating. This thesis was conducted in the framework of a close partnership between IMS Laboratory, the GIE III-V lab, who is themain French founder of III-V semiconductor devices for electronic and photonic applications,and THALES Research & Technology in Palaiseau. An in-depth characterization and analysiswork has addressed thermal aspects that contribute, in particular, to limit the optical outputpower of a laser diode. In such a context, we have carried out a set of complementary characterizations both at III-V lab and IMS allowing us to provide some corrective solutionsfor technological optimization concerning the etching depth of the grooves that defines the emitting stripe of the laser diode and the nature of the submount acting as a thermocompensator.These solutions have been proposed from optical modelling implemented with a dedicated simulator, property of III-V lab, and thermal and thermomechanical (multiphysics approach) finite element simulations of the overall microassembled structure. All this work has resulted in the fabrication as well as electro-optical and thermal characterizations of three vertical structures namely LOC (Large Optical Cavity), SLOC (Super Large Optical Cavity)and AOC (Asymmetrical Optical Cavity). The LOC and SLOC vertical structures have been processed with a Fabry-Perot cavity and also including a Bragg grating (DFB architecture) while the AOC one was only fabricated with a Fabry-Perot cavity. State-of-the-art results aredemonstrated since in particular an optical power of 8W with an efficiency of 60% has been obtained that can be compared to those recently published by the Ferdinand-Braun Institute.The originality of the work carried out in this PhD has allowed us to receive a grant from the European Laserlab Cluster (The Integrated Initiative of the European Laser Research Infrastructures), to conduct dedicated experiments at the Max-Born Institute (Berlin) in thegroup of Dr. J.W. Tomm. The work aimed to characterize mechanical strain of the laser diode induced by the soldering process. Two vertical structures (SLOC and AOC) were investigated using complementary techniques (microphotoluminescence, time-resolved photoluminescence,photocurrent spectroscopy and pulsed L-I measurements), allowing to quantify the level of residual stress provided by the laser diode mounting process as well as the kinetics of the catastrophic degradation process (COD)., Cette thèse CIFRE adresse le développement de diodes laser, émettant à 975nm, de très forte puissance, rendement à la prise élevé, et stabilisées en longueur d’onde pour pompage de fibres dopées Er/Yb et réalisation de lasers à fibre. La thèse a été développée dans le cadre d’un partenariat étroit entre le Laboratoire IMS, le GIE III-V Lab, principal fondeur français de composants à semiconducteurs III-V pour des applications électroniques et photoniques, et THALES Research & Technology à Palaiseau en région parisienne. Un travail en profondeur de caractérisation et d’analyse a porté sur les aspects thermiques qui contribuent, en particulier,à limiter les niveaux de puissance optique de sortie. Dans ce cadre, nous avons réalisé un ensemble de caractérisations complémentaires au GIE III-V lab et à l’IMS nous permettant d’envisager des solutions correctives d’optimisation technologique portant en particulier sur la profondeur de gravure définissant la largeur de la zone d’émission et la nature du substrat dissipateur. Ces solutions ont été proposées à partir de modélisations physiques mises en oeuvre avec un simulateur dédié, propriété de III-V Lab et de simulations par éléments finis thermiques et thermomécaniques (approche multiphysique) de la structure microassemblée définitive. Ces travaux se sont prolongés par la fabrication et la caractérisation électro-optique et thermique de plusieurs structures verticales : LOC (Large Optical Cavity), SLOC (Super Large OpticalCavity) et AOC (Asymetrical Optical Cavity). Les diodes laser de type LOC et SLOC sont stabilisées en longueur d’onde en intégrant un réseau de Bragg (DFB). Une puissance optique de 8W avec une efficacité de 60% a été obtenue ; ce qui permet de situer ces travaux à l’état de l’art international notamment vis-à-vis de ceux publiés par l’Institut Ferdinand-Braun.L’originalité des travaux menés dans cette thèse nous a permis d’avoir accès à une bourse du Cluster européen « Laserlab » (The Integrated Initiative of European Laser Research Infrastructures), pour conduire des campagnes d’expérimentation à l’Institut Max Born à Berlin dans le groupe du Dr J.W. Tomm. Les travaux ont porté sur la caractérisation thermique de ces diodes laser de forte puissance émettant à 975nm, à double hétérostructure symétrique et asymétrique (SLOC et AOC), en utilisant des techniques complémentaires (microphotoluminescence,photoluminescence résolue en temps, spectroscopie de photocourant et mesures L-I pulsées) et permettant d’évaluer le type de contraintes résiduelles apportées par les étapes de report de la diode Laser ainsi que la cinétique de dégradation catastrophique de type COD.

The goal of this thesis work was to characterise quantum dots obtained by a novel growth method. We used microphotoluminescence techniques to study multiple properties of these dots. We have evaluated main contributions to light-heavy hole valence band mixing. Contrary to self-assembled dots, we find a more homogeneous distribution of the mixing parameter, which can be explained by the absence of mechanical tension due to lattice mismatch. We have also measured magneto-optical parameters such as electron and hole g-factors, diamagnetic shift, fine structure splitting for bright and dark states. These results allowed us to estimate geometric parameters of dots, making a point on the growth quality. Polarisation studies on the dark states have revealed a result different from previous theoretical predictions. We have used a recently presented model to explain our findings. The last part of this work presents results on quantum dots embedded in an n-i Schottky structure. We have measured binding energies of positive and negative trions, to make a connection with previous results, to then study double quantum dot system. We have observed an anticrossing of hole S states, which is in agreement with our estimations based on sample parameters.; Le but de cette thèse a été de caractériser des boîtes quantiques obtenues avec une nouvelle méthode de croissance. Utilisant des techniques de microphotoluminescence, nous avons étudié les différentes contributions au mélange des bandes de trous lourds et de trous légers. En l'absence de contrainte, la distribution du paramètre de mélange est plus homogène ; cependant, d'autres contributions deviennent dominantes et nous les avons discutées. Nous avons mesuré les paramètres magnéto-optiques : facteurs Landé de l'électron et du trou, décalage diamagnétique, paramètres de structure fine des états noirs et brillants. Les valeurs obtenues ont permis d'estimer la variation des paramètres géométriques des boîtes, ce qui est lié à la qualité du contrôle de la croissance. La polarisation des états noirs mesurée s'est révélée différente de celle prévue selon le modèle utilisé précédemment dans la littérature. Utilisant un modèle théorique récent, nous avons reproduit nos observations, ce qui met en évidence une modulation possible de la polarisation des états noirs par le champ magnétique. Finalement, nous avons effectué des études de contrôle de charges dans des structures n-i Schottky. Pour des boîtes uniques, des états multichargés ont été observés. Nous avons mesuré les énergies de liaison des trions positif et négatif, au préalable à une étude sur des molécules de boîtes. Nous avons observé des anticroisements des états S des trous dans deux boîtes, en accord avec nos prévisions basées sur les paramètres nominaux de l'échantillon.

Brotons-Gisbert, Mauro et al., Manipulating properties of matter at the nanoscale is the essence of nanotechnology, which has enabled the realization of quantum dots, nanotubes, metamaterials, and two-dimensional materials with tailored electronic and optical properties. Two-dimensional semiconductors have revealed promising perspectives in nanotechnology. However, the tunability of their physical properties is challenging for semiconductors studied until now. Here we show the ability of morphological manipulation strategies, such as nanotexturing or, at the limit, important surface roughness, to enhance light absorption and the luminescent response of atomically thin indium selenide nanosheets. Besides, quantum-size confinement effects make this two-dimensional semiconductor to exhibit one of the largest band gap tunability ranges observed in a two-dimensional semiconductor: from infrared, in bulk material, to visible wavelengths, at the single layer. These results are relevant for the design of new optoelectronic devices, including heterostructures of two-dimensional materials with optimized band gap functionalities and in-plane heterojunctions with minimal junction defect density., This work was supported by the Spanish Government (Grant Nos. TEC2014-53727-C2-1-R and MAT2014-53500-R as well as Grants FIS2015-64886-C5-3-P and FIS2015-64886-C5-4-P), the Comunidad Valenciana Government (Grant No. PROMETEOII/ 2014/059), and the Generalitat de Catalunya Government (2014SGR301). The work at Berkeley was supported by National Science Foundation No. DMR-1306601. Authors thank the Central Support Service for Experimental Research (SCSIE) (SEM and Micro-PL facilities) of the University of Valencia. J.F.S.R. acknowledges financial support from the Mobility Program of VLC-CAMPUS. E.C., G.T., F.H., and P.O. acknowledge support of the Spanish MINECO through the Severo Ochoa Centers of Excellence Program under Grants SEV-2015-0496 and SEV-2013-0295. F.H. acknowledges support of CONACYT. M.B.G. acknowledges his fellowship no. UVINV-PREDOC13-110538 under the program “Atracció de Talent, VLC-CAMPUS” of the University of Valencia. D.A.P. acknowledges his contract CPI-15-276 under the program PROMETEOII/2014/059.

This thesis addresses the light-matter interaction in nitride nanostructures embedded inoptical microcavities. By using micro-photoluminescence experiments, we study the optical propertiesof GaN/AlN quantum dots embedded in planar microcavities and those of GaN/AlNquantum wells in AlN microdisks. By placing quantum dots in planar microcavities, we are ableto modify the emission diagram and increase the collection efficiency. The design of the microcavitiesis optimized by using numerical simulations based on transfer matrix method with aninternal emitter. For an AlN microcavity with AlN/AlGaN Bragg mirrors, we show that the collectionefficiency could be theoretical increase by one order of magnitude, which is confirmed byour micro-photoluminescence experiments on single quantum dots. This observation opens theway for advanced studies such as photon correlations experiments in the UV range. The secondpart of our work is devoted to the realization of a micro-laser operating in the deep-UV range atroom-temperature. By using thin GaN/AlN quantum wells (2.8 monolayers), grown on siliconsubstrate and embedded in AlN microdisks, we observe a laser emission at 275 nm under pulsedoptical pumping. This demonstration shows the strong potentiality for future developments ofnitride-on-silicon nano-photonics.; Cette thèse porte sur l’interaction lumière-matière au sein de nanostructures placées dansdes cavités optiques à base de semi-conducteurs nitrures. A l’aide d’expériences de microphotoluminescencedans l’ultra-violet, nous étudions les propriétés optiques de boîtes quantiquesGaN/AlN dans des microcavités planaires et celles de puits quantiques GaN/AlN insérés dansdes microdisques AlN. Afin d’améliorer la collection du faible signal de photoluminescence deboîtes quantiques uniques, nous utilisons des microcavités planaires pour modifier le diagrammed’émission d’une boîte quantique. Le dessin des microcavités est optimisé grâce à des simulationsnumériques basées sur la méthode des matrices de transfert en présence d’un émetteur.Nous montrons que, pour une microcavité nitrure à base de miroirs de Bragg AlN/AlGaN, lacollection des photons émis par une boîte quantique peut être théoriquement améliorée d’unordre de grandeur, ce qui est confirmé par nos mesures sur boîtes quantiques uniques, ouvrantainsi la voie à des études avancées de corrélations de photons dans l’UV. La seconde partiedes travaux est dédiée à la réalisation d’un micro-laser opérant dans l’UV profond et à températureambiante. En utilisant des puits quantiques GaN/AlN de 2,8 mono-couches, crûs sursubstrat silicium et insérés dans des microdisques AlN, nous observons une émission laser à275 nm sous pompage optique impulsionnel. Cette démonstration montre le fort potentiel dessemi-conducteurs nitrures pour la nano-photonique UV sur silicium.

Results of experimental study of multiexcitonic emission related to the p-shell of single self-assembled InAs/GaAs quantum dots are presented. Optical properties of a first emission line to appear from the p-shell of a strongly excited quantum dots are investigated using low-temperature polarization- sensitive micro-photoluminescence measurements. The emission line is attributed to the recombination of a complex of three electrons and holes confined in a dot (neutral triexciton), 3X. It is found that the emission consists of two linearly polarized components and the fine structure splitting is larger than the respective splitting of a neutral exciton. The optical anisotropy of the 3X emission is related to the anisotropy of the quantum dot localizing potential. The axis of the 3X optical anisotropy changes from dot to dot covering broad range within ±50 degrees with respect to the axis defined by the optical anisotropy of a neutral exciton (X). Possible origin of the deviation is discussed.

We investigated lateral charge carrier transport in indium gallium nitride InGaN/GaN multi-quantum wells for two different samples, one sample emitting green light at about 510 nm and the other emitting cyan light at about 470 nm. For the cyan light emitting sample we found a diffusion constant of 1.2 cm2/s and for the green light emitting sample 0.25 cm2/s. The large difference in diffusion constant is due to a higher point defect density in the green light emitting quantum wells (QWs) as high indium incorporation tends to reduce material quality.

We have studied the coherence properties of one electron-pair state confined in a single quantum dot (QD). Two kinds of dots are studied: monolayer step-induced GaAs QDs and self-organized InAs QDs. In order to probe at resonance the excitonic intrinsic properties, the QDs are embedded in a one-dimensional waveguide. The QD luminescence is then collected from the top surface of the waveguide, so that we can separate photons coming from excitation and luminescence. Firstly, We demonstrate the existence of a strong coupling regime between a single QD and light pulses by observing Rabi oscillations of the micro-photoluminescence as a function of the pulse area. Secondly, the electron-hole pair can be driven by a pair of phase-tailored pulses in a coherent control experiment. Depending on the relative phase between the two pulses, constructive or destructive interferences can enhance or destroy the QD emission during the coherence time. Two interesting coupling regimes have been investigated. The case of an excitation with π-pulses allows to measure lifetimes, T1, of excited states, whereas π/2-pulses are used to measure the coherence time, T2, of the fundamental transition. The results show that the total decoherence time T2 (170 ps) is comparable to the effective exciton lifetime T1 (200 ps) although not reaching the upper theoretical limit of 2T1. We conclude that energy relaxation and pure dephasing processes due to virtual scattering with phonons contribute on an equal footing to the loss of coherence.; Nous avons étudié les propriétés de cohérence d'une paire électron-trou confinée dans une boîte quantique (BQ) unique. Ce travail a été réalisé sur deux types de BQs : d'une part, des BDs de GaAs sur GaAlAs obtenues par fluctuations d'épaisseur aux interfaces, et d'autre part, des BQs auto-organisées d'InAs sur GaAs. Afin d'exciter de manière résonnante la transition fondamentale de BQs, celles-ci sont insérées dans un guide d'onde unidimensionnel. La luminescence des BQs est collectée par la surface du guide d'onde, de telle façon à séparer la luminescence du laser diffusé. Tout d'abord, nous avons observé des oscillations de Rabi sur l'intensité de la micro-photoluminescence en fonction de l'aire de l'impulsion lumineuse d'excitation. Ceci démontre l'existence d'une régime de couplage fort entre une BQ unique et l'impulsion. Deuxièmement, une paire électron-trou peut être manipuler par un train de deux impulsions, dans une expérience dite de contrôle cohérent. En fonction de la différence de phase entre les deux impulsions, des interférences constructives ou destructives entrainent, respectivement, une augmentation ou une diminution de l'intensité de la luminescence de la BQ. Nous avons montré que deux impulsions π permettent de mesurer le temps de vie, T1, de l'état excité et deux impulsions π/2 sont utilisées pour mesurer le temps de cohérence, T2. Les résultats expérimentaux montrent que le temps de décohérence total, T2 (170 ps), est du même ordre de grandeur que le temps de vie T1 (200 ps) bien que le limite supérieure de 2T1 ne soit pas atteinte. Nous en concluons que la perte de cohérence est autant dû à l'émission spontanée qu'aux processus de déphasage pur.

We have studied the coherence properties of one electron-pair state confined in a single quantum dot (QD). Two kinds of dots are studied: monolayer step-induced GaAs QDs and self-organized InAs QDs. In order to probe at resonance the excitonic intrinsic properties, the QDs are embedded in a one-dimensional waveguide. The QD luminescence is then collected from the top surface of the waveguide, so that we can separate photons coming from excitation and luminescence. Firstly, We demonstrate the existence of a strong coupling regime between a single QD and light pulses by observing Rabi oscillations of the micro-photoluminescence as a function of the pulse area. Secondly, the electron-hole pair can be driven by a pair of phase-tailored pulses in a coherent control experiment. Depending on the relative phase between the two pulses, constructive or destructive interferences can enhance or destroy the QD emission during the coherence time. Two interesting coupling regimes have been investigated. The case of an excitation with π-pulses allows to measure lifetimes, T1, of excited states, whereas π/2-pulses are used to measure the coherence time, T2, of the fundamental transition. The results show that the total decoherence time T2 (170 ps) is comparable to the effective exciton lifetime T1 (200 ps) although not reaching the upper theoretical limit of 2T1. We conclude that energy relaxation and pure dephasing processes due to virtual scattering with phonons contribute on an equal footing to the loss of coherence.; Nous avons étudié les propriétés de cohérence d'une paire électron-trou confinée dans une boîte quantique (BQ) unique. Ce travail a été réalisé sur deux types de BQs : d'une part, des BDs de GaAs sur GaAlAs obtenues par fluctuations d'épaisseur aux interfaces, et d'autre part, des BQs auto-organisées d'InAs sur GaAs. Afin d'exciter de manière résonnante la transition fondamentale de BQs, celles-ci sont insérées dans un guide d'onde unidimensionnel. La luminescence des BQs est collectée par la surface du guide d'onde, de telle façon à séparer la luminescence du laser diffusé. Tout d'abord, nous avons observé des oscillations de Rabi sur l'intensité de la micro-photoluminescence en fonction de l'aire de l'impulsion lumineuse d'excitation. Ceci démontre l'existence d'une régime de couplage fort entre une BQ unique et l'impulsion. Deuxièmement, une paire électron-trou peut être manipuler par un train de deux impulsions, dans une expérience dite de contrôle cohérent. En fonction de la différence de phase entre les deux impulsions, des interférences constructives ou destructives entrainent, respectivement, une augmentation ou une diminution de l'intensité de la luminescence de la BQ. Nous avons montré que deux impulsions π permettent de mesurer le temps de vie, T1, de l'état excité et deux impulsions π/2 sont utilisées pour mesurer le temps de cohérence, T2. Les résultats expérimentaux montrent que le temps de décohérence total, T2 (170 ps), est du même ordre de grandeur que le temps de vie T1 (200 ps) bien que le limite supérieure de 2T1 ne soit pas atteinte. Nous en concluons que la perte de cohérence est autant dû à l'émission spontanée qu'aux processus de déphasage pur.

This thesis is dedicated to the strong coupling regime between excitons and photons at room temperature in bulk ZnO-based microcavities grown on Si (111) substrate by molecular beam epitaxy. A preliminary theoretical study shows that the continuum absorption of excitonic resonances is responsible for the observed strong damping on the upper polariton branch, without affecting the lower polariton branch. The strong coupling regime, at room temperature, of the cavity mode and the Bragg modes of the microcavity is then demonstrated by angle-resolved spectroscopy. Moreover, we observe the presence of a bottleneck on the Bragg mode polariton branch. The latter may be suppressed by increasing the exciton density or the temperature. We compare our experimental results with recent theoretical predictions and discuss the achievement of the polariton laser regime.; Cette thèse est consacrée au couplage fort exciton-photon à température ambiante dans les microcavités massives à base de ZnO élaborées par épitaxie par jets moléculaires sur substrat Si(111). Une étude théorique préliminaire montre que le continuum d'absorption des résonances excitoniques est responsable du fort amortissement observé sur la branche haute de polaritons, sans toutefois affecter la branche basse de polaritons. Le couplage fort à température ambiante du mode de cavité ainsi que des modes de Bragg de la microcavité a ensuite été démontré par spectroscopie résolue en angle. De plus, nous observons la présence d'un goulot d'étranglement (bottleneck) sur le mode de Bragg de polaritons. Ce dernier peut être supprimé en faisant varier la densité d'excitons ou la température. Nous comparons nos résultats expérimentaux aux prévisions théoriques faites en vue de l'obtention d'un régime laser à polaritons.

7th International Conference on Physics of Ligh-Matter Coupling in Nanostructures (PLMCN7), Havana, CUBA, APR 12-17, 2007; International audience; By means of an original all-optical experimental technique using microphotoluminescence in a waveguiding geometry, resonant coherent manipulation of quantum states in a single quantum dot becomes possible now. Resonant Rabi oscillation of the fundamental exciton state in a single quantum dot has been realized. We present the results obtained on two different kinds of samples: InAs/GaAs self-assembled quantum dots and naturally formed GaAs quantum dots by thickness fluctuations. (C) 2008 Published by Elsevier Ltd.

Over the past few decades, III-V nitrides have attracted much attention due to the possibility to realize high efficiency optoelectronic devices covering all the UV and visible part of the light spectrum. However, the device fabrication has gone much faster than the understanding of the physical phenomena occurring in these materials. In this context, we propose a system for prototypical studies of low dimensional excitons in III-nitride materials based on single polar Stranski-Krastanow (SK) GaN/AlN quantum dots. Here, the demonstration of single dot spectroscopy is performed in three stages dealing with the issues related to instrumentation, sample design and optical measurements, successively. First, a state of the art microphotoluminescence setup operating in the UV light spectrum has been built. The system exhibits diffraction limited sub micron excitation laser spot size and spatial resolution. The performances of the developed setup have been successfully tested through the characterization of III-nitride heterostructures and devices. The second stage is dedicated to the sample development and preparation. Special emphasis was given to the SK growth mode transition and the parameters influencing the QD formation. It has been seen that when using standard growth conditions the achievement of samples suitable for single dot spectroscopy, namely small QDs with low areal density, is quite difficult. We show that this problem can been circumvented by promoting the material kinetics over the sample surface. As a result of the allowed material redistribution, the final sample exhibits AlN step edges covered by numerous large dots that leave place to a low density small quantum dots found over the AlN terraces. In-depth optical spectroscopic studies of single polar GaN/AlN quantum dots are carried out by means of low-temperature micro-photoluminescence. Luminescence linewidths as low as 590 µeV are obtained allowing a thorough characterization of the QD electronic properties. The measured linewidths at low temperature still exhibit a large inhomogeneous broadening, which is studied in order to demonstrate the decreasing effect of the quantum confined Stark effect with the dot size reduction. Biexciton emission is observed for a wide range of dot size. It is shown that the binding energy ( Ebxx ) exhibits two regimes. The main one is governed by the dot height through the quantum confined Stark effect leading to a variation of Ebxx from + 10 meV for the smallest dots down to -11 meV for the largest ones. A secondary variation of opposite sign is demonstrated for dots having the same height but different lateral size. Finally, our most recent studies allow reporting the first observation of excited levels in any III-nitride quantum dot system. The lowest energy excited states are found to originate from the lateral confinement of heavy holes. In addition, when two excitons are present in the dots the permutations of the determined excitonic states give rise to three biexciton states characterized by four luminescence transitions.

The aim of this ph-D thesis was to study by spectrophotometry coupling phenomenon between single emitters such as InAs/GaAs quantum dots inside an optical microcavity tailored to the emitter. The purpose was to propose and to demonstrate the potential of several microcavities' original geometries. In this manuscript, we will start from the growth's description of such structures by Molecular Beam Epitaxy (MBE) to focus on three different proposals of innovative geometries for which we will both describe the technological process leading to their manufacturing, as well as the optical studies performed to demonstrate their potential. For example, microdisks directly bonded to sapphire showed very interesting thermal dissipation leading to amazing properties for microlasers. On Bragg mirrors micropillars, we have shown for the first time that those structures were able to sustain both high-Q whispering-gallery modes and lateral standard micropillars modes, as well as the ability to use those modes as lasing modes, which open new possibilities in term of microphotonic devices. We also developed a specific reproducible Au-coating technique and studied its effect on the micropillars modes, showing that no degradation of the optical properties of the pillar due to the metal occurred, leading to the possibility to use this technique for various specific applications. Finally, we propose and demonstrate the potential of using a single quantum dot inserted in a monolithic nanowire for its very high collection efficiency, showing that this kind of structure could be a very serious competitor to the usual geometry used for single photon sources, the micropillar., Ce travail de thèse porte sur l'étude par spectrophotométrie de phénomènes de couplage entre un émetteur photonique discret et une cavité optique dont les propriétés sont adaptées à l'émetteur. Nous nous sommes intéressés à l'interaction de boîtes quantiques semiconductrices InAs/GaAs avec des microcavités optiques dont la géométrie originale diffère selon les propriétés dont on veut tirer partie. Ainsi, nous partirons de la fabrication de ces systèmes par épitaxie par jets moléculaires, pour nous focaliser sur trois grands types de microcavités, dont nous décrirons à la fois les étapes de fabrication, mais aussi les études optiques réalisées par spectrophotométrie Infra-rouge. Ainsi, les microdisques reportés sur saphir par collage moléculaire ont montré un important potentiel pour la réalisation de microlasers, grâce à de très bonnes propriétés de dissipation thermique. Sur les micropiliers à miroirs de Bragg, nous avons expérimentalement montré pour la première fois la co-existence de modes de galerie et de modes de micropiliers, ainsi que la possibilité d'exploiter l'effet laser sur ces modes, ce qui ouvre de nouvelles perspectives en termes de systèmes photoniques. Nous avons également développé une technique originale et reproductible de métallisation à l'or des flancs et démontré son innocuité sur les propriétés optiques de ces modes, ce qui permet d'envisager son application à d'autres dispositifs. Enfin, nous terminons par la fabrication et l'étude de nano-fils photoniques à boîtes quantiques uniques, dont les capacités prometteuses permettent de conclure à une concurrence sérieuse vis-à-vis des micropiliers en tant que source de photon unique.