Coherent control of excited state populations in rubidium using Rabi oscillations

Complete population inversion is demonstrated analytically in the strong-field limit in a three-level system using the rubidium 5s–5p–5d transition. We exploit the pre-transients of an amplitude-shaped laser pulse to direct the dynamics of the Rabi oscillations such that the population transfer to the excited state can be controlled in a wide range from a strongly enhanced to vanishing one. The excitation is performed under off-resonant conditions. During the intense ultrafast pulse, levels shift to such an extent that two-photon resonant excitation becomes possible, even though a frequency spectrum does not contain photons with energies necessary for the excitation of an unperturbed system. Within the reach of experimental parameters, we demonstrate 70% population transfer.