  A coherent coupling among different energy photons provided by nonlinear
optical interaction is regarded as a photonic version of the Rabi oscillation.
Cavity enhancement of the nonlinearity reduces energy requirement significantly
and pushes the scalability of the frequency-encoded photonic circuit based on
the photonic Rabi oscillation. However, confinement of the photons in the
cavity severely limits the number of interactable frequency modes. Here we
demonstrate a wide-bandwidth and efficient photonic Rabi oscillation achieving
full-cycle oscillation based on a cavity-enhanced nonlinear optical interaction
with a monolithic integration. We also show its versatile manipulation beyond
the frequency degree of freedom such as an all-optical control for polarizing
photons with geometric phase. Our results will open up full control accessible
to synthetic dimensional photonic systems over wide frequency modes as well as
a large-scale photonic quantum information processing.
