Control of exciton relaxation channels in quantum dot molecules

We observe modulations in radiative lifetimes and intensities of the spatially indirect exciton as the InAs/GaAs coupled quantum dot system is tuned between molecular and atomic like states. With standard time-resolved single photon counting techniques the measured lifetimes were found to vary between 0.3 and 2.0 ns which resulted in modulations of the observed photoluminescence intensity of the indirect exciton. These modulations can be attributed to phonon mediated relaxations and carrier tunneling processes in good agreement with the modeled results. We clearly see the structure of the acoustic phonon distribution as shown in recent theoretical predictions. Tuning the relative energy levels in coupled quantum dots results in controllable modulation of exciton relaxation channels that may provide new directions in engineering decoherence in these systems.