  Optomechanical systems provide a pathway for the bidirectional
optical-to-microwave interconversion in (quantum) networks. We demonstrate the
implementation of this functionality and non-adiabatic optomechanical control
in a single, $\mu$m-sized potential trap for phonons and exciton-polariton
condensates in a structured semiconductor microcavity. The exciton-enhanced
optomechanical coupling leads to self-oscillations (phonon lasing) -- thus
proving reversible photon-to-phonon conversion. We show that these oscillations
are a signature of the optomechanical strong coupling signalizing the emergence
of elusive phonon-exciton-photon quasiparticles -- the phonoritons. We then
demonstrate full control of the phonoriton spectrum as well as coherent
microwave-to-photon interconversion using electrically generated GHz-vibrations
and a resonant optical laser beam. These findings establish the
zero-dimensional polariton condensates as a scalable coherent interface between
microwave and optical domains with enhanced microwave-to-mechanical and
mechanical-to-optical coupling rates.
