  Quantum emitters with a $\Lambda$-type level structure enable numerous
protocols and applications in quantum science and technology. Understanding and
controlling their dynamics is, therefore, one of the central research topics in
quantum optics. Here, we drive two-photon Rabi oscillations between the two
ground states of cesium atoms and observe the associated oscillatory Raman gain
and absorption that stems from the atom-mediated coherent photon exchange
between the two drive fields. The atoms are efficiently and homogeneously
coupled with the probe field by means of a nanofiber-based optical interface.
We study the dependence of the two-photon Rabi frequency on the system
parameters and observe Autler-Townes splitting in the probe transmission
spectrum. Beyond shedding light on the fundamental processes underlying
two-photon Rabi oscillations, our method could also be used to investigate
(quantum) correlations between the two drive fields as well as the dynamical
establishment of electromagnetically induced transparency.
