Piezoelectric phononic integrated circuits

Piezoelectric microresonators have revolutionized modern wireless communication. While billions of these devices are in widespread use across a range of frequencies, materials, and device geometries, every piezoelectric microresonator in current use shares one common characteristic: they all manipulate (quasi) plane waves. While the ideas around waveguiding and strong confinement of acoustic fields have been around since the early days of ultrasonics research, they have had relatively little impact on modern devices. Building on recent developments in related fields, in particular integrated photonics and quantum computing, we outline the prospects for piezoelectric phononic integrated circuits, which can manipulate gigahertz acoustic waves in micrometer-scale waveguide geometries in low-loss chipscale platforms. We also discuss the main roadblocks, with an emphasis on insertion loss, which need to be addressed for these devices to have the desired impact on future systems.