  We present an open-system master equation study of the coherent and
incoherent resonance fluorescence spectrum from a two-level quantum system
under coherent pulsed excitation. Several pronounced features which differ from
the fluorescence under a constant drive are highlighted, including a multi-peak
structure and a pronounced off-resonant spectral asymmetry, in stark contrast
to the conventional symmetrical Mollow triplet. We also study semiconductor
quantum dot systems using a polaron master equation, and show how the key
features of dynamic resonance fluorescence change with
electron--acoustic-phonon coupling.
