AC Stark shift in CdSSe-doped glasses and spectral relaxation in CdTe quantum dots

摘要

We present femtosecond resolution measurements that demonstrate the occurrence of the ac Stark effect in glass samples doped with CdSSe nanocrystallites. The sample is excited by a 50 fs pulse 80 meV below the band edge. The absorption edge shifts tracking the profile of the pumping pulse. At intensities below 0.5 GW/cm$+2$/ the edge shift is linear in the pump intensity. Above this value the shift tends to saturate. We also studied CdTe quantum dots in a glass matrix excited resonantly with the 1S - 1S transition. In this case we observe the dynamics of hole relaxation in the valence band. The hole population equilibrates with a time constant of less than 100 fs.