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Abstract

The transient-absorption spectrum of a $V$-type three-level system is
investigated, when this is periodically excited by a train of equally spaced,
$\delta$-like pump pulses as, e.g., from an optical-frequency-comb laser. We
show that, even though the probe pulse is not assumed to be much shorter than
the pump pulses, light-induced states appear in the absorption spectrum. The
frequency- and time-delay-dependent features of the absorption spectra are
investigated as a function of several laser control parameters, such as the
number of pump pulses used, their pulse area, and the pulse-to-pulse phase
shift. We show that the frequencies of the light-induced states and the
time-delay-dependent features of the spectra contain information on the action
of the intense pulses exciting the system, which can thus complement the
information on light-imposed amplitude and phase changes encoded in the
absorption line shapes.