We report on cw optical experiments performed in a semiconductor microcavity containing a single quantum well in the strong coupling regime. Angularly resolved photoluminescence measurements under non-resonant excitation show the collapse of a relaxation bottleneck as the excitation power is increased. As a result, the emission close to k_{∥}=0 presents a non-linear behavior. In a two-beam experiment we resonantly inject polaritons at k_{∥}=0 and show that relaxation from states with large in-plane wave vector toward k_{∥}=0 is stimulated by the polariton final state population.
The micro-photoluminescence of GaAs/AlAs type II double quantum well structure is presented. The specific band alignment of the investigated system allows obtaining high concentration of long lived carriers. This enables us to study diffusion of carriers and/or indirect excitons. It was found that the carrier flow does not follow the classical diffusion equation and is driven by the potential modification due to the presence of photo created carriers.
The nature of sharp emission lines which are present in macro-luminescence experiments on a type-II GaAs/AlAs double quantum well structure is discussed. The experiments, which also include micro-lumines- cence measurements, allowed us to conclude that the sharp emission lines observed originate from lateral GaAlAs islands of a fewμm in diameter. They serve as efficient type-I recombination centers for indirect excitons and/or carriers which diffuse in the GaAs/AlAs QW structure and strongly affect the emission processes observed in macro-luminescence experiments. These traps can easily be filled with electron-hole pairs, giving rise to the formation of neutral excitons as well as more complex excitonic molecules. Magneto-luminescence spectra from single islands resemble those observed for natural quantum dots formed in narrow GaAs quantum wells.
We study polarization resolved correlation between photons emitted in cascaded biexciton-exciton recombination from a single quantum dot formed in type II GaAs/AlAs bilayer. Magnetic field induced transition from anisotropy controlled to the Zeeman controlled emission was demonstrated by a circular polarization correlation between the emitted photons. A simple model describing the effect allowed us to determine the anisotropic exchange splitting of the excitonic state. This method of the anisotropic exchange splitting determination can be useful in the case when other methods are not sensitive enough.
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