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

摘要

Abstract: 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. !6