  A variety of nonequilibrium multi-pulse states can emerge in a mode-locked
laser through the interactions between the quasi-continuous-wave background
(qCWB) and optical pulses inside the laser cavity. However, they have been long
regarded as unpredictable and hardly controllable due to the noise-like nature
of the qCWB, and relevant previous studies thus lack a clear understanding of
their underlying mechanisms. Here, we demonstrate that the qCWB landscape can
be manipulated via optoacoustically mediated interactions between the qCWB and
mode-locked pulses, which dramatically alters the behaviors of multi-pulse
dynamics in unprecedented manners. In this process, impulsive qCWB modulations
are created at well-defined temporal locations, which act as the point emitters
and attractive potentials for drifting pulse bunches and soliton rains. Hence,
we can transport a single pulse bunch from a certain temporal position to
another on the qCWB, and also make the soliton rain created and collided
exclusively at specific temporal locations, in sharp contrast to the
conventional cases. Our study opens up new possibilities to control the
nonequilibrium multi-pulse phenomena precisely in the time domain, which would
not only help the observation and clear understanding of undiscovered features
of multi-pulse dynamics but offer a practical means of advanced optical
information processing.
