We investigate the population and dephasing kinetics of a quantum dot coupled by Auger and phonon scattering processes with a femtosecond-pulse- excited electron-hole plasma in a quantum well or wetting layer. For the two-dimensional (2D) plasma we treat the quantum kinetics of the Coulomb scattering processes with a two-time-dependent screened Coulomb interaction potential. Additionally the scattering with LO phonons is included. For ultrashort pulse excitations close to the band edge of the plasma we obtain a slow decay of the polarization of the quantum dot with superimposed oscillations whose frequency is given by the energetic distance of the quantum dot levels and the 2D band edge. For two-pulse excitations we calculate the absorption spectrum of the probe pulse for various delay times and pump pulse intensities. One sees, e.g., the buildup of gain for a strong pump pulse in the spectral regions below the dot absorption line and below the band edge of the plasma. In the calculated four-wave-mixing signal we find in addition to long dephasing times, which decrease with increasing 2D plasma densities, also oscillations due to the beating of the quantum dot and the band edge transitions.
|Original language||English (US)|
|Journal||Physical Review B - Condensed Matter and Materials Physics|
|State||Published - May 16 2006|
ASJC Scopus subject areas
- Electronic, Optical and Magnetic Materials
- Condensed Matter Physics