Homogeneous linewidth of confined electron-hole-pair states in II-VI quantum dots

We present results of nanosecond-hole-burning experiments of small CdSe and ${\mathrm{CdS}}_{1\mathrm{-}\mathit{x}}$${\mathrm{Se}}_{\mathit{x}}$ quantum dots embedded in glass at various temperatures. The spectral width of the holes exhibits a complex interplay between excitation conditions and illumination history. Among a great variety of investigated II-VI quantum dots in glasses from various sources, we find, after strong laser illumination, samples showing spectrally narrow holes similar to those reported for quantum dots embedded in organic matrices with interfaces well defined by organic groups. These sharp nonlinear resonances with a halfwidth Γ of only 10 meV at T=20 K allow one to investigate the energetic distance of the lowest hole levels and the temperature dependence of the homogeneous line broadening. The differences in the linewidth in the hole-burning spectra are attributed to changes of interface charge states or interface polarizations under high excitation.