Ultrafast coherent carrier control in quantum wells

We report the coherent control of excitons in quantum wells with pairs of 150-fs infrared pulses. Oscillations in the exciton density versus inter-pump-pulse separation, which correspond to the resonant transition energy, yield new insight into coherent exciton dynamics when their phase is analyzed. We demonstrate that these oscillations are caused when the second laser pulse destroys or enhances excitons that were created by the first pulse. The coherent carrier destruction generates ultrafast exciton dynamics that are not limited by the linewidth of the optical transition.