  Fabry-Perot microcavities can strongly enhance interactions between light and
molecules, leading to the formation of hybrid light-matter states known as
polaritons. Polaritons possess much smaller effective masses and much larger
group velocities when the molecules are resonant with cavity modes that have
finite (non-zero) in-plane wavevectors, giving rise to the possibilities of
long-range and ultrafast ballistic transport. In this paper, we present results
of numerical simulations of the ultrafast ballistic transport phenomenon in
real space and time during and after initialization with a short, spatially
localized pulse. We find that the transport of the molecular excitons as
induced by the external light field is synchronized with the evolution of the
enhanced and localized electromagnetic field inside the cavity. Moreover, the
synchronized transport rate is in good agreement with the group velocities
predicted from a calculated dispersion relation across a wide range of
frequencies. These simulations provide an intuitive tool for understanding the
collective motion of light and excitons and helps to better understand how
experimental observations of polaritons should be interpreted.
