Benoit Deveaud
Ecole Polytechnique Federale de Lausanne, Physique, Faculty Member
Abstract Summary form only given. We present time resolved pump and probe measurements, in the strong excitation regime, of a semiconductor microcavity (MC) containing quantum wells (QWs). The fundamental QW exciton (X) and the cavity... more
Abstract Summary form only given. We present time resolved pump and probe measurements, in the strong excitation regime, of a semiconductor microcavity (MC) containing quantum wells (QWs). The fundamental QW exciton (X) and the cavity mode were resonant or slightly detuned, while the energy of the laser photons was chosen to be dose to the energy of the photon like polariton. The investigated MCs are high finesse heterostructures made of GaAs/GaAlAs layers, featuring cavity-mode line widths of at most ...
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Abstract Summary form only given. Quartz tuning forks, driven to electromechanical resonance by piezo elements, are widely used as distance sensing elements in scanning near-field optical microscopy (SNOM). Distance controls, based on... more
Abstract Summary form only given. Quartz tuning forks, driven to electromechanical resonance by piezo elements, are widely used as distance sensing elements in scanning near-field optical microscopy (SNOM). Distance controls, based on tuning forks without piezo elements, have been successfully employed in atomic force microscopes. We extended this technique to the case of low temperature SNOM. In our experimental set-up, the fibre is fixed at two points.
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Abstract Summary form only given. The strong coupling between quantum well excitons and cavity photons leads to the appearance of a new type of quasi-particles, the so-called microcavity polaritons. The energy dispersion of polaritons is... more
Abstract Summary form only given. The strong coupling between quantum well excitons and cavity photons leads to the appearance of a new type of quasi-particles, the so-called microcavity polaritons. The energy dispersion of polaritons is very sharp owing to the photon component. At the same time, the polaritons are strongly interacting due to the exciton-exciton interaction and saturation. In this contribution, we present a microscopic theory for the nonlinear optics of the polariton matter: microscopic equations are presented for two ...
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Abstract: InGaAs quantum-well complex-coupled DFB lasers with gain coupling induced by vertical emission are demonstrated. Continuous-wave operation of these lasers at room temperature provides single-mode emission at a wavelength around... more
Abstract: InGaAs quantum-well complex-coupled DFB lasers with gain coupling induced by vertical emission are demonstrated. Continuous-wave operation of these lasers at room temperature provides single-mode emission at a wavelength around 980 nm. A spectral linewidth as narrow as 15 MHz and a side-mode suppression ratio larger than 40 dB are obtained. The use of this gain coupling mechanism permits to reduce the influence of the regrown interface quality on the laser performance. OCIS codes:(140.3490) Lasers, ...
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Abstract Summary form only given. The importance of LO phonon emission for intersubband scattering (ISBS) processes is now well established. In very good agreement with theoretical expectations, such a process gives scattering times of 1... more
Abstract Summary form only given. The importance of LO phonon emission for intersubband scattering (ISBS) processes is now well established. In very good agreement with theoretical expectations, such a process gives scattering times of 1 ps or less. The situation is different in wide quantum wells, when the energy separation ΔE 12 between the first two subbands is smaller than hω LO. It has often been proposed that ISBS should then be mediated mainly by acoustical phonons, and be quite slow. Such wells would then be promising for laser ...
Research Interests: Physics, Laser, IEEE, Electron, Time Resolved, and 6 moreLuminescence, Phonon, Femtosecond, Scattering, Quantum Well, and Excitation
Abstract. We report the growth of a staircase solid state photomultiplier structure. The device is obtained by a combination of ternary AlGaSb and quaternary GaInAsSb graded layers epitaxied on GaSb substrates, using molecular beam... more
Abstract. We report the growth of a staircase solid state photomultiplier structure. The device is obtained by a combination of ternary AlGaSb and quaternary GaInAsSb graded layers epitaxied on GaSb substrates, using molecular beam epitaxy. The different layers used in the structures have been individually optimized for their electrical and optical quality. A multiplication coefficient of 7, without excess noise, is estimated on a six-step device, for a maximum voltage of only 15 V.
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Abstract Pump and Probe measurements with femtosecond pulses are performed on a Gain-Clamped Semiconductor Optical Amplifier (a special laser structure). The relaxation oscillations of the carriers density are observed directly in the... more
Abstract Pump and Probe measurements with femtosecond pulses are performed on a Gain-Clamped Semiconductor Optical Amplifier (a special laser structure). The relaxation oscillations of the carriers density are observed directly in the time domain. Reasonable values of the differential gain and the nonlinear gain factors are extracted from the current dependence of the oscillations.
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Abstract. We have observed strong oscillations in the time-resolved emission of a semiconductor microcavity, excited non-resonantly with circularly-polarized light pulses. When the cavity is optically driven into a non-linear emission... more
Abstract. We have observed strong oscillations in the time-resolved emission of a semiconductor microcavity, excited non-resonantly with circularly-polarized light pulses. When the cavity is optically driven into a non-linear emission regime, the period of the oscillations amounts to~ 30 ps, independently of the angle of observation. The angular dependence of the emission, at a negative detuning of-13 meV, shows that although the cavity starts emitting with maximum intensity at K~ 0 cm-1, the intensity is rapidly ...
D. BLOCK, B. BOULANGER, R. ROMESTAIN, B. DEVEAUD*, B. LAMBERT* and A. REGRENY* ... Laboratoire de Spectrornetrie Physique, BP 87 et Celphyra, CNRS-UA 09, F-38402 Saint-Martin-d'H6res Cedex, France *CNET/LAB/ICM, BP 40, F-22301 Lamion... more
D. BLOCK, B. BOULANGER, R. ROMESTAIN, B. DEVEAUD*, B. LAMBERT* and A. REGRENY* ... Laboratoire de Spectrornetrie Physique, BP 87 et Celphyra, CNRS-UA 09, F-38402 Saint-Martin-d'H6res Cedex, France *CNET/LAB/ICM, BP 40, F-22301 Lamion Cedex, France ... Abstract: We report studies of photoexcited carrier dynamics in GaAlAs/GaAs superlattices as a function of excitation power using optical technique. At low power, we observe a quadratic behavior of luminescence intensity, due to competition between electron-hole ...
The effects of background n-and p-type doping on Zn diffusion in GaAs/AlGaAs multilayered structures are investigated by secondary-ion-mass spectrometry and photoluminescence measurements. Zn diffusions are performed at 575 C into... more
The effects of background n-and p-type doping on Zn diffusion in GaAs/AlGaAs multilayered structures are investigated by secondary-ion-mass spectrometry and photoluminescence measurements. Zn diffusions are performed at 575 C into Si-doped, Be-doped, and Si/Be-codoped identical GaAs/Al 0.2 Ga 0.8 As multiple-quantum-well structures. The results obtained by secondary-ion-mass spectrometry show that the Zn diffusion induces an enhancement of Be out-diffusion and the disordering of all structures. ...
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After the first demonstration of Bose Einstein condensation in the solid state in 2006 and the establishment of exciton polariton condensates in the wider scientific community, an intense interest has been attracted by this phenomenon at... more
After the first demonstration of Bose Einstein condensation in the solid state in 2006 and the establishment of exciton polariton condensates in the wider scientific community, an intense interest has been attracted by this phenomenon at both theoretical and experimental level. It is the object of this thesis to follow on from the demonstration of polariton condensation and to study more in detail different aspects of fundamental importance related to the polariton condensation. This thesis initially presents the basic concepts for excitons, polaritons and condensates in and out of equilibrium. The following part focuses on the presentation of the experimental methods. The thesis is separated in two conceptual parts, one for the experiments under continuous wave excitation and one that was dedicated to the dynamical properties of polariton condensates. The appearance of a single condensate despite the presence of disorder is initially presented with the study of the mode synchronization of neighboring condensates. Then the coexistence of multiple condensates is demonstrated, a phenomenon that had previously passed unperceived due to the noise of the excitation laser. The use of a low noise excitation source reveals spectral characteristics that were "hidden" in the previously broad spectra and a detailed experimental analysis is performed in order to study the full real and momentum space distribution of the individual condensates and their long range spatial coherence. Interferometric measurements which give access to the long range spatial coherence and the condensate phase, revealed the existence of pinned singularities. These were further investigated and were identified as the commonly known singly quantized vortices, here shown for the first time in a polariton condensate. Up to this point most of the studies demonstrated that the polarization of polariton condensates was preferentially linearly polarized. A more detailed analysis that was pursued in this thesis showed that the degree of linear polarization is not necessarily high but there are regions on the sample where it is rather poor. In certain areas where we do not observe a lift of degeneracy in polarization, the polariton condensates have to be considered as spinor objects. This unique property permitted the first observation of the celebrated case of fractional vortices which constitute the elementary excitations of spinor superfluids. In the second part of the thesis the work is focused on the dynamics of polariton condensates. Beginning with the dynamics of singly quantized vortices, it is shown that vortices present traceable in time trajectories from their nucleation positions all the way to their pinning locations. Finally taking advantage of the inherent disorder of the sample, a naturally occurring coupled double well system is investigated. The observation of oscillating polariton currents between the two wells was demonstrated. This phenomenon is analogous to the well known Josephson oscillations. Most -if not all- of the studied phenomena are a complex interplay of the disorder, the driven-dissipative character of the polariton condensates and the nonlinearities occurring in the system. A detailed theoretical analysis that supports the observed experimental findings is finally provided
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Reference EPFL-CONF-171959View record in Web of Science Record created on 2011-12-16, modified on 2017-05-12
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Summary form only given. The strong coupling between quantum well exciton and cavity photon leads to the so-called microcavity polaritons whose energy dispersion is very sharp due to the photon component. Unlike bare excitons, the optical... more
Summary form only given. The strong coupling between quantum well exciton and cavity photon leads to the so-called microcavity polaritons whose energy dispersion is very sharp due to the photon component. Unlike bare excitons, the optical response of polaritons is very sensitive to the incidence angle of the exciting laser beams. This means that the dispersive character can drastically affect nonlinear wave-mixing processes. We present new results about nonlinear wave-mixing due to polariton-polariton correlations. In particular, we consider an angle-resolved pump-probe experiment where the probe is assumed at normal incidence, while the pump has a finite incidence angle. The polariton-polariton correlations are taken into account through a microscopic Hamiltonian treatment including exciton-exciton interaction.
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Abstract The occurrence of Rabi flopping in excitonic transitions of semiconductors demonstrate that an intense light field can induce a non-perturbative ac Stark effect despite the very fast excitation-induced dephasing. However the... more
Abstract The occurrence of Rabi flopping in excitonic transitions of semiconductors demonstrate that an intense light field can induce a non-perturbative ac Stark effect despite the very fast excitation-induced dephasing. However the homogeneous broadening induced by the strong excitation prevented the observation in quantum wells of the spectral counterpart of Rabi oscillations in time, the ac Stark splitting. We report the evolution of the absorption spectrum of a specially designed single InGaAs quantum well as a function of ...
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We present a theoretical analysis of experimental photoluminescence spectra in highly excited semiconductor quantum wires. We show that the inclusion in the theory of electron–hole correlations strongly modifies the shape of emission... more
We present a theoretical analysis of experimental photoluminescence spectra in highly excited semiconductor quantum wires. We show that the inclusion in the theory of electron–hole correlations strongly modifies the shape of emission spectra at any density. We discuss the role of these correlations in the evaluation of the band gap renormalization. The calculated energy-and density-dependence of the broadening agree qualitatively with the experimental results. The broadening is also comparable in magnitude to the band gap ...
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Abstract We have studied the mechanisms of capture in quantum wells by time resolved luminescence with femtosecond resolution. The measured decay times of the barrier luminescence are always shorter than 3 ps and the well luminescence... more
Abstract We have studied the mechanisms of capture in quantum wells by time resolved luminescence with femtosecond resolution. The measured decay times of the barrier luminescence are always shorter than 3 ps and the well luminescence rise time is of the order of 4 ps at 100 K. These coupled results indicate that electron and hole capture is always very fast. We carry out a quantum mechanical calculation which takes into account LO phonon scattering and impurity scattering as well as hot carrier effects. The short ...
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HAL - hal.archives-ouvertes.fr, CCSd - Centre pour la Communication Scientifique Direct. Accueil; Dépôt: S'authentifier; S'inscrire. Consultation: Par domaine; Les 30 derniers dépôts; Par année de publication, rédaction, dépôt;... more
HAL - hal.archives-ouvertes.fr, CCSd - Centre pour la Communication Scientifique Direct. Accueil; Dépôt: S'authentifier; S'inscrire. Consultation: Par domaine; Les 30 derniers dépôts; Par année de publication, rédaction, dépôt; Par type de publication; Par collection; Les portails de l'archive ouverte HAL; Par établissement (extraction automatique); ArXiv; Les Thèses (TEL). Recherche: Recherche simple; Recherche avancée; Accès par identifiant; Les Thèses ...
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We have studied experimentally and modelled theoretically the capture properties and transport mechanisms of electrons and holes in laser structures. We describe first the extreme case where the barrier thickness is very large: then... more
We have studied experimentally and modelled theoretically the capture properties and transport mechanisms of electrons and holes in laser structures. We describe first the extreme case where the barrier thickness is very large: then semiclassical drift-diffusion equations may be applied and quantum-mechanical effects at the edge of the well are negligible. A second extreme case occurs when the barrier is narrow enough for quantum mechanics to apply fully. There, strong variations of the capture time with the well width ...
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The dynamics of carrier capture and intersubband relaxation in GaAs quantum well have been measured, using a time-resolved photoluminescence technique. At low carrier densities (≤ 2× 10 10 cm-2), electron capture times are shown to... more
The dynamics of carrier capture and intersubband relaxation in GaAs quantum well have been measured, using a time-resolved photoluminescence technique. At low carrier densities (≤ 2× 10 10 cm-2), electron capture times are shown to oscillate as a function of well width and a quantum-mechanical resonance is observed when one confined level is 36 meV below the barrier edge. Holes capture times are fast (< 10 ps), and depend weakly on the structure. No significant changes of the carrier capture times are observed for carrier ...
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Research Interests: Materials Engineering, Physics, Condensed Matter Physics, Chemistry, Kinetics, and 15 moreMonte Carlo, Quantum Mechanics, Medicine, Mathematical Sciences, Physical sciences, Band Gap, Luminescence, Electron Transport, Optical physics, Room Temperature, American physical society, Quantum Well, Simulation experiment, Superlattices, and Relaxation Time
We report the optical determination of exciton binding energies in small-period GaAs/Ga0.7Al0.3As superlattices by means of low-temperature photoluminescence excitation spectroscopy and photoluminescence spectroscopy as a function of... more
We report the optical determination of exciton binding energies in small-period GaAs/Ga0.7Al0.3As superlattices by means of low-temperature photoluminescence excitation spectroscopy and photoluminescence spectroscopy as a function of temperature. The heavy-hole exciton binding energy decreases with decreasing superlattice period. Our experimental findings are in reasonable agreement with a variational calculation.
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Abstract.-We study by time-resolved luminescence, with subpicosecond resolution, the tunnelling processes out of a narrow well (NW) coupled to a wider one 0by a thin barrier. Resonance and nonresonance between the first level of the NW... more
Abstract.-We study by time-resolved luminescence, with subpicosecond resolution, the tunnelling processes out of a narrow well (NW) coupled to a wider one 0by a thin barrier. Resonance and nonresonance between the first level of the NW and the second level of the WW is obtained by adjusting the WW width. At resonance, and for narrow enough barriers, the transfer of the electrons to the WW ground state takes about 2ps and is analogous to LO phonon-assisted intersubband relaxation. When the barrier thickness is increased, even ...
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Exciton-polaritons, mixed light-matter quasiparticles in semiconductors, have recently shown evidence for Bose-Einstein condensation. Some of the properties of condensates of exciton-polaritons are reviewed in this article. We first... more
Exciton-polaritons, mixed light-matter quasiparticles in semiconductors, have recently shown evidence for Bose-Einstein condensation. Some of the properties of condensates of exciton-polaritons are reviewed in this article. We first discuss the spontaneous appearance of long-range order and the way this can be easily accessed in the case of polariton fluids. We show that the Penrose-Onsager criterion is valid even for such a very special case of condensate. We then describe the experiments that allow observation of topological defects in the fluid: quantized vortices, half vortices, and hyperbolic spin vortices. We demonstrate through the comparison with the gross Pitaevskii equation that the appearance and stability of such vortices are linked with the dissipative nature of the condensate together with the presence of disorder. We then briefly summarize the experiments on superfluid behavior of the polaritons at large-enough densities and expand somewhat more on the dynamical behav...
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We report the first observation of stochastic resonance in confined exciton-polaritons. We evidence this phenomena by tracking the polaritons behavior through two stochastic resonance quantifiers namely the spectral magnification factor... more
We report the first observation of stochastic resonance in confined exciton-polaritons. We evidence this phenomena by tracking the polaritons behavior through two stochastic resonance quantifiers namely the spectral magnification factor and the signal-to-noise ratio. The evolution of the stochastic resonance in function of the modulation amplitude of the periodic excitation signal is studied. Our experimental observations are well reproduced by numerical simulations performed in the framework of the Gross-Pitaevskii equation under stochastic perturbation.