The irreversible decay of coherent intersubband polarizations in n-type modulation-doped GaAs/AlxGa1-xAs quantum wells is studied by femtosecond time-integrated and time-resolved four-wave mixing. We provide the first direct evidence for predominant homogeneous broadening of intersubband resonances by intraband electron-electron scattering. Even at a low electron concentration of 5×1010 cm-2 the dephasing time T2=320 fs accounts fully for the 4 meV intersubband linewidth. For 6×1011 electrons/cm2 and strong excitation, athermal electron distributions show enhanced dephasing rates.
|Original language||English (US)|
|Journal||Physical Review B - Condensed Matter and Materials Physics|
|State||Published - 2001|
ASJC Scopus subject areas
- Electronic, Optical and Magnetic Materials
- Condensed Matter Physics