  Polaritons enable the resonant coupling of excitons and photons to vibrations
in the application-relevant super high frequency (SHF, 3-30 GHz) domain. We
introduce a novel platform for coherent optomechanics based on the coupling of
exciton-polaritons and electrically driven SHF longitudinal acoustic phonons
confined within the spacer region of a planar Bragg microcavity. An intrinsic
property of the microcavity platform is the back-feeding of phonons via
reflections at the sample boundaries, which enables frequency x quality factors
products exceeding 10^14 Hz as well as huge modulation amplitudes of the
optical transition energies (up to 8 meV). We show that the modulation is
dominated by the phonon-induced energy shifts of the excitonic polariton
component, thus leading to an oscillatory transition between the regimes of
weak and strong light-matter coupling. These results open the way for
polariton-based coherent optomechanics in the non-adiabatic, side-band-resolved
regime of coherent control.
