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 φ between the pulses. Compared to the case of a train of independent pulses (i.e., mutually incoherent), a pulse sequence with $\phi =0\mathrm{}$ is shown to be sensitive to dispersion for lower optical depths, whereas a pulse sequence with $\phi =\pi$ is shown to be more robust.