Interference between femtosecond pulses observed via time-resolved spontaneous fluorescence

We study spontaneous fluorescence excited by a series of phase-controlled femtosecond pulses in an inhomogeneously broadened medium containing a frequency comb of sharp spectral holes. We show that evolution of the spontaneous fluorescence on picosecond time scale is sensitive to interference between the excitation pulses and that varying the relative phase between the excitation pulses changes the time evolution of the fluorescence.