Coherent light-matter interaction in InGaAs quantum dots: Dephasing time and optical Rabi oscillations

We present measurements of the dephasing time and of optical Rabi oscillations in the excitonic ground-state transition of an InGaAs quantum dot ensemble at low temperature, using an heterodyne pump-probe technique. Dephasing times of several hundred picoseconds are measured, enabling coherent light-matter interaction with picosecond optical pulses. Optical Rabi oscillations which are damped versus pulse area and change period when changing pulse duration are observed. Comparison with calculations indicates that the observed damping is not intrinsic to a single dot. Dephasing processes and the biexciton resonance change the amplitude and the period of the oscillations, respectively, while the damping versus pulse area is due to a distribution of transition dipole moments in the ensemble