Resonant interaction between an ultrashort pulse train and a two-level system: frequency domain analysis

We investigate the problem of two-level atoms driven by an ultrashort pulse train in the frequency domain. At low intensity regime, we obtain a perturbative analytical solution that allows us to discuss the role of the mode number of the frequency comb near or at resonance on the temporal evolution of the atomic coherence. At high intensities, the effect of the number of modes is analyzed in the steady-state regime through numerical calculations.