Giant optomechanical coupling and dephasing protection with cavity exciton-polaritons

Electronic resonances can significantly enhance photon-phonon coupling but are normally avoided in cavity optomechanics due to absorption losses and dephasing by inhomogeneous broadening. We demonstrate experimentally that exciton-polaritons in semiconductor microcavities enable single-particle resonant optomechanical couplings with GHz vibrations reaching record values in the tens of MHz range. Moreover, this resonant enhancement is protected from inhomogeneous broadening by the Rabi gap. Single-polariton nonlinearities and the optomechanical strong-coupling regime become accessible in this platform.