Time-resolved spontaneous emission of excitons in a microcavity: Behavior of the individual exciton-photon mixed states

Interplay between strong coupling and radiative damping of excitons and surface plasmon polaritons in hybrid nanostructures

We report on the interplay between strong coupling and radiative damping of strongly coupled excitons (Xs) and surface plasmon polaritons (SPPs) in a hybrid system made of J-aggregates and metal nanostructures. The optical response of the system is probed at the field level by angle-resolved spectral interferometry. We show that two different energy transfer channels coexist: coherent resonant dipole-dipole interaction and an incoherent exchange due to the spontaneous emissions of a photon by one emitter and its subsequent reabsorption by another. The interplay between both pathways results in a pronounced modification of the radiative damping due to the formation of super- and subradiant polariton states. This is confirmed by probing the ultrafast nonlinear response of the polariton system and explained within a coupled oscillator model. Such a strong modification of the radiative damping opens up interesting directions in coherent active plasmonics.

Nonlinear emission dynamics of a GaAs microcavity with embedded quantum wells

The emission dynamics of a GaAs microcavity at different angles of observation with respect to the sample normal under conditions of nonresonant picosecond-pulse excitation is measured. At sufficiently high excitation densities, the decay time of the lower polariton emission increases with the polariton wavevector; at low excitation densities the decay time is independent of the wavevector. The effect of additional nonresonant continuous illumination on the emission originating from the bottom of the lower polariton branch is investigated. The additional illumination leads to a substantial increase in the emission intensity (considerably larger than the intensity of the photoluminescence excited by this illumination alone). This fact is explained in terms of acceleration of the polariton relaxation to the radiative states due to scattering by charge carriers created by the additional illumination. The results obtained show that, at large negative detunings between the photon and exciton modes, polariton-polariton and polariton-free carrier scattering are the main processes responsible for the filling of states near the bottom of the lower polariton branch.

Coherent generation of acoustic phonons in an optical microcavity

Ultrafast coherent generation of acoustic phonons is studied in a semiconductor optical microcavity. The confinement of the light pulse amplifies both the generation and the detection of phonons. In addition, the standing wave character of the photon field modifies the generation and detection phonon bandwidth. Coherent generation experiments in an acoustic nanocavity embedded in an optical microcavity are reported as a function of laser energy and incidence angle to evidence the separate role of the optical and exciton resonances. Amplified signals and phonon spectra modified by the optical confinement are demonstrated.

Polariton and spin dynamics in semiconductor microcavities under non-resonant excitation

Semiconductor microcavities offer an ideal scenario to study strong radiation-matter interactions. In this paper we review the temporal dynamics of polaritons in II-VI and III-V based microcavities under non-resonant excitation conditions. We present evidence of final-state stimulated scattering and discuss the spin-dependent emission, which exhibits a remarkably rich behaviour.

Electron-polariton scattering in semiconductor microcavities

In semiconductor microcavities, electron-polariton scattering has been proposed as an efficient process that can drive polaritons from the bottleneck region to the ground state, achieving Bose amplification of the optical emission. We present clear experimental observation of this process in a structure that allows control of the electron density and we report substantial enhancement of photoluminescence. We show that this enhancement is more effective at higher temperatures due to the different way that electron scattering processes either broaden or relax polaritons.

Negatively charged quantum well polaritons in a GaAs/AlAs microcavity: An analog of atoms in a cavity

The negatively charged exciton (X-) is observed to strongly couple with the microcavity- (MC-)confined photons in a GaAs quantum well containing a two-dimensional electron gas with 0<n(e)</=3x10(10) cm(-2). This strong coupling results in a formation of charged polaritons. The coupling strength is found to depend on sqrt[n(e)], in analogy to two-level atoms in a cavity. The analysis of the reflection and photoluminescence spectra shows that X- is strongly admixed with the neutral exciton via their coupling with the MC photons. The linewidth dependence on n(e) indicates that electron-polariton scattering is effective.