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We have studied micro-photoluminescence spectra of self-assembled single GaAs/AlGaAs quantum dots (QDs). Under non-resonant optical excitation, a single GaAs QD exhibits several sharp peaks in the PL spectra whose origins are the recombination of neutral or charged multi-excitonic complexes. In single photon correlation measurements, photons emitted from charged biexcitons and charged excitons show bunching which indicates that photon pairs are generated from the cascade recombination of the charged biexcitons. The result of polarization correlation measurements shows that each photon of the pairs is polarized linearly and orthogonally. These polarization features can be understood by the superposition of elliptically polarized photons affected by the electron–hole exchange interaction in the anisotropic QD.

Four-wave mixing (FWM) technique is used to study the phonon induced dephasing of the excitons in CdTe self-assembled quantum dots. The FWM signals show two different decay structures with fast and slow decay components, indicating a non-Lorentzian line-shape with a zero-phonon line and a broadband from exciton–acoustic phonon interaction in the spectral region. The dephasing of the zero-phonon line and the sideband components both show non-linear characteristics with respect to temperature. The experimental data are reproduced well by a theoretical model taking into account the carrier–acoustic phonon coupling.

The photoluminescence from localized excitons in In 0.25 Ga 0.75 N was enhanced up to 6.6 times by approaching a gold nano-particle to nano-meter vicinity. Mapping images of enhanced photoluminescence and topological images were measured simultaneously with a spatial resolution of 100 nm. With an improved measurement system and selection of relatively flat area of the sample, we propose that the segregated metallic In droplet ought to play an important role for the present tip-enhance effect.

Excitation intensity dependence of photoluminescence signals is observed in Cd 0.9 Mn 0.1 Te at 2 K with varying exciton density from 10 14 to 10 19 cm −3 . For intermediate density regime ( 16 cm −3 ) , the transient spectral shift reflecting the magnetic polaron formation is found to decrease with an increase in density. For high-density regime (>10 17 cm −3 ) , the polaron shift disappears, and the density-dependent red shift caused by the band-gap renormalization is observed. The experimental findings demonstrate that the magnetic polaron is unstable at high-density condition.

We present time resolved photoluminescence measurements of GaAs/Al /sub 0.3/Ga/sub 0.7/As quantum dot structures where no wetting layer is connecting the dots. We show that the two-dimensional character of the wetting layer is not relevant in determining the quantum dot capture, in contrast with the conclusions of several models so far presented in the literature.