Phase control of dispersion effects for an ultrashort pulse train propagating in a resonant medium

We present here a theoretical analysis of the propagation of a sequence of ultrashort pulses in an optically dense medium. The interaction is resonant and treated in the weak-field, regime. Dispersion is dominant and induces important reshaping effects. We show that these effects depend crucially on the relative phase shift, phi between the pulses. Compared to the case of a train of independent pulsed (i.e., mutally incoherent), a pulse sequence with phi = 0 is shown to be sensitive to dispersion,for lower optical depths, whereas a pulse sequence with phi = pi is shown to be more robust.