Projekt A.5: Collective carrier dynamics in spatially and spectrally inhomogeneous environment

We study experimentally and theoretically a population-inverted, coupled 0D-2D system and focus on quantum coherence and decoherence. We analyze pulse shapes via cross-correlation methods and apply heterodyne FWM and pump-probe spectroscopy. The 0D-2D interaction shall be controlled via electrical/optical carrier injection in the 2D varying there carrier density, excess energy or temperature. The spectrally inhomogeneous environment is given by the inhomogeneous broadening of the 0D-energy states. The spatially inhomogeneous environment is given by both well width fluctuations and spatial distribution/density of 0D-confining potentials. In particular we address the following problems:
(i) A population inverted 0D-system (QDs in the gain regime) shall be driven into Rabi oscillations and the coherence lifetime shall be derived for different carrier injection currents and pump detunings, in particular when pumping the 2D on- and off-resonant to the 0D-continuum states; (ii) The possibility to engineer dephasing times in the interacting 0D-2D system shall be explored; (iii) Transitions between localized and extended reservoir states shall be optically excited and the impact on 0D-states dynamics shall be studied. The question whether 0D-states become increasingly coupled via (nonequilibrium) excitation of shared 2D-states will be addressed.
The experiments are to be accompanied by numerical calculations of the time evolution of coherence and carrier populations in the 0D-probe states while the 2D-states are electrically/optically populated.

Project leaders: Prof. Dr. U. Woggon [1], Prof. Dr. A. Knorr [2], Prof. Dr. E. Schöll [3]