Benoît Marie Joseph Deveaud

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We study the subpicosecond gain dynamics in a high-finesse semiconductor microcavity containing quantum wells by means of degenerate pump-probe spectroscopy. Tuning the optical excitation in resonance with both the exciton and the cavity modes, at high pump fields the probe pulses are strongly amplified near the energy of the empty-cavity mode. At zero probe delay, integration of the probe spectrum yields a net gain of several percents. The coherent nature of the gain is demonstrated by its oscillatory beha

Condensation of exciton polaritons in semiconductor microcavities takes place despite in-plane disorder. Below the critical density, the inhomogeneity of the disorder limits the spatial extension of the ground state. Above the critical density, in the presence of weak disorder, this limitation is spontaneously overcome by the nonlinear interaction, resulting in an extended synchronized phase. In the case of strong disorder, several non-phase-locked condensates can be evidenced. The transition from a synchro

We study exciton and biexciton spectra in disordered semiconductor quantum wires by means of nanophotoluminescence spectroscopy. We demonstrate a close link between the exciton localization length along the wire and the occurrence of a biexciton spectral l ...

Luminescence spectra of V-groove GaAs/AlGaAs quantum wires are investigated by spatially resolved photoluminescence (PL) spectroscopy using a low temperature scanning near-field optical microscope (SNOM). The statistical analysis of these spectra in terms of the autocorrelation function reveals the presence of level repulsion. We find that the comparison between the experimental autocorrelation curve and the theoretical one obtained from the simulation of PL spectra, assuming for each exciton state a Lorent

Photoluminescence lifetimes of the n = 2 level in a large quantum well show a clear nonmonotonic dependence on the density of optically generated carriers. Varying the power density over five orders of magnitude we prove directly the high efficiency of carrier-carrier interaction for intersubband scattering when longitudinal-optical phonon emission is suppressed. For low densities, the observed n = 2 decay times get shorter (from 40 down to 5 ps) as the density is increased. At high densities Pauli blocking

Intraband transitions around 1.5 mum are studied in PbSe quantum dots at room temperature. Femtosecond pump-probe measurements reveal induced absorption by photoexcited carriers up to higher energy levels and its relaxation. A dominant decay component has a decay time of 10-40 ps, which is determined by the relaxation of carriers at the lowest absorption peak. The induced absorption is observed in a broad spectral range between 0.77 and 2.5 eV.

A dynamical theory of multiphoton transitions in semiconductors is developed using a density matrix approach. It is shown that, in dipole approximation, these transitions require a mixed parity of the basis stales and that band-diagonal coupling's of the electromagnetic field to Bloch electrons have to be included. The general theory is outlined using the simple, but solvable model of a diatomic tight-binding chain. Possible extensions and applications of the approach are discussed.

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.

The optical speed-up at transparency principle has been successfully applied to a gain-clamped semiconductor optical amplifier yielding a remarkable acceleration in the gain recovery of the device as well as to the disappearance of the typical relaxation oscillations stemming from the coupling between the internal lasing mode and the carrier density. A record gain recovery time of 13 ps has been measured with an available gain of still 16 dB. A small-signal analysis of the semiconductor laser amplifier rate

In this work we present the coherent control of polariton parametric scattering with weak phase locked probe pulses. It is demonstrated that the signal emission arising from the parametric scattering is completely coherent for moderate excitation power, whereas at high pump density the dynamics appears less coherent due to the depletion of the pump polariton reservoir. It is furthermore demonstrated that the phase of the probe pulses controls the emission from signal, pump, and idler at the same time.

We report on the effect of noise on the characteristics of the bistable polariton emission system. The present experiment provides a time-resolved access to the polariton emission intensity. We evidence the noise-induced transitions between the two stable ...

We perform quantum tomography on one-dimensional polariton condensates, spontaneously occurring in linear disorder valleys in a CdTe planar microcavity sample. By the use of optical interferometric techniques, we determine the first-order coherence functio ...

We have studied the femtosecond dynamics of excitonic resonances in quantum well microcavities under strong excitation. Very strong non-linearities are observed, which bear clear resemblance to the non-linearities of an atomic two-level system. The fact that the excitonic system undergoes Rabi flopping and AC Stark splitting is clearly evidenced in a number of cases. Excitation induced dephasing shows an effect much stronger than the light dressing and prevents the observation of the Rabi flopping only when

The experimental investigation of spontaneously created vortices is of utmost importance for the understanding of quantum phase transitions towards a superfluid phase, especially for two-dimensional systems that are expected to be governed by the Berezinski-Kosterlitz-Thouless physics. By means of time-resolved near-field interferometry we track the path of such vortices, created at random locations in an exciton-polariton condensate under pulsed nonresonant excitation, to their final pinning positions impo

It is demonstrated that during the first few picoseconds after resonant femtosecond excitation the secondary radiation from a strongly coupled semiconductor microcavity containing one quantum well is dominated by Rayleigh scattered light. At early times after excitation (10 ps) the lower polariton branch provides the most intense emission which is due to incoherent luminescence.

We investigate the mechanisms leading to the optical non-linearities observed on a strongly excited semiconductor microcavity containing quantum wells. This study of a coupled exciton-cavity system is possible owing to the availability of a sample of exceptionally high quality, permitting to exclude effects of disorder and inhomogeneous broadening. Sub-picosecond pump and probe experiments are performed, in the regime of an incoherent exciton gas of high density. For such a gas the dephasing due to collisio

Exciton polaritons have been shown to be an optimal system in order to investigate the properties of bosonic quantum fluids. We report here on the observation of dark solitons in the wake of engineered circular obstacles and their decay into streets of qua ...

We report on the mechanism of hopping for bound excitons under an energy gradient. By means of a Monte-Carlo simulation, we show that this mechanism explains the movement of bound excitons observed experimentally. We show that the speed of the excitons dec ...

We propose a new configuration for semiconductor optical amplifiers (SOAs), called optical speed-up at transparency (OSAT), which allows to speed up the gain recovery of SOAs and their saturation power without sacrificing the gain, nor increasing the applied current, The proposed configuration is particularly well-suited for high-speed WDM or OTDM applications, It consists of an optical cw-signal injected at the transparency point of the SOA, This setup is potentially integrable on a single chip, and still

We have directly measured, under operating conditions, the distributions of carrier densities and temperatures in a gain-clamped semiconductor optical amplifier designed for operation at 1.55 mum. As expected, longitudinal spatial hole burning is much smaller than in conventional semiconductor optical amplifiers and the effects of gain clamping are clearly evidenced. The amplifier nevertheless shows a sizeable temperature increase for both the lattice and the carriers at high currents, which are attributed

Benoît Marie Joseph Deveaud

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Net coherent optical gain in strongly pumped semiconductor microcavities

Synchronized and Desynchronized Phases of Exciton-Polariton Condensates in the Presence of Disorder

Localization-dependent photoluminescence spectrum of biexcitons in semiconductor quantum wires

Photoluminescence spectra and level repulsion in quantum wires

Density dependence of carrier-carrier-induced intersubband scattering in GaAs/AlxGa1-xAs quantum wells

1.5-mu m intraband transitions in PbSe quantum dots

Dynamical density matrix theory of multiphoton transitions in semiconductors

Direct observation in the temporal domain of relaxation oscillations in a semiconductor laser

Acceleration of a gain-clamped semiconductor optical amplifier by the optical speed-up at transparency scheme

Coherence properties of polaritons in semiconductor microcavities

Effect of a noisy driving field on a bistable polariton system

Penrose-Onsager Criterion Validation in a One-Dimensional Polariton Condensate

Femtosecond dynamics and non-linearities of exciton-photon coupling in semiconductor microstructures

Probing the Dynamics of Spontaneous Quantum Vortices in Polariton Superfluids

Resonant Rayleigh scattering versus incoherent luminescence in semiconductor microcavities

Intrinsic non-linearities in exciton-cavity-coupled systems

Soliton Instabilities and Vortex Street Formation in a Polariton Quantum Fluid

Hopping process of bound excitons under an energy gradient

Extremely fast high-gain and low-current SOA by optical speed-up at transparency

Density clamping and longitudinal spatial hole burning in a gain-clamped semiconductor optical amplifier