  We simulate the transient absorption of attosecond pulses of
infrared-laser-dressed atoms by considering a three-level system with the
adiabatic approximation. The delay-dependent interference features are
investigated from the perspective of the coherent interaction processes between
the attosecond pulse and the quasi-harmonics. We find that many features of the
interference fringes in the absorption spectra of the attosecond pulse can be
attributed to the coherence phase difference. However, the modulation signals
of laser-induced sidebands of the dark state is found related to the population
dynamics of the dark state by the dressing field.
