Phononic integrated circuit*

The hallmark of a photonic integrated circuit is the utilization of high-index-contrast optical waveguides to route photons and to form complex photonic circuits on a planar chip without creating suspended structures. Despite many similarities between optical and acoustic waves, phononic waveguides analogous to planar optical waveguides remain elusive to the research community, preventing the formation of phononic integrated circuits with a complexity on par with the photonic counterpart. Here we experimentally realize such a phononic integrated circuit architecture through exploiting GaN-on-sapphire platforms which provide efficient confinement and routing of phonons in the top layer. By demonstrating the key building blocks of the phononic circuits, the scalability of this platform and its full analogy to photonic circuits are firmly established. Such phononic integrated circuits will play an important role in the upcoming hybridized phononic chips for manipulating, transferring, storing, and converting classical and quantum information.