Nanophotonic cavity optomechanics with propagating acoustic waves at frequencies up to 12 GHz

Strong coherent interactions between colocalized optical and mechanical eigenmodes of various cavity optomechanical systems have been explored intensively toward quantum information processing using both photons and phonons. In contrast to localized modes, propagating mechanical waves are another form of phonons that can be guided and manipulated like photons in engineered phononic structures. Here, we demonstrate sideband-resolved coupling between multiple photonic nanocavities and propagating surface acoustic waves up to 12 GHz. Coherent and strong photon-phonon interaction is manifested with electro-optomechanically induced transparency, absorption, and amplification, and phase-coherent interaction in multiple cavities. Inside an echo chamber, it is shown that a phonon pulse can interact with an embedded nanocavity for multiple times. Our device provides a scalable platform to optomechanically couple phonons and photons for microwave photonics and quantum photonics.