Optimal pump-dump control Original Research Article

A density matrix formulation of quantum control is developed to treat the joint optimization of two ultrafast, phase-unlocked laser fields in the weak response and strong response regimes. For the situation in which the frequency spectra of the two fields do not overlap, a coupled pair of control equations can be derived. These equations are then solved iteratively to determine the pair of pump-dump fields that best drives a material system to a desired objective. A novel method is presented to perform an ensemble average over the random phase between the two control fields. As a numerical example of the formalism, we present calculations on the pump-dump control of vibrational wave packets in the iodine molecule in gas phase. We show that a selected, highly excited vibrational wave packet can be created on the ground electronic state with simple, experimentally achievable laser pulses. Such wave packets might be used as initial states for the subsequent control of chemical processes, or spectroscopic observables.