Toward efficient GHz frequency acoustic wave injection in μ m-scale unsuspended geometries: A case study in ScAlN on silicon-on-sapphire
Year: 2026
Type: article
Abstract: Focusing GHz frequency acoustic fields into and out of wavelength (μm) scale unreleased waveguide geometries with near-unity efficiency is of potential interest in a variety of problems ranging from building chip-scale microwave to optical photon transducers and integrated RF front-ends. In scenarios requiring co-propagating light fields or extremely low mechanical dissipation, the acoustic fields are routed in a high refractive index semiconductor layer-like silicon, with a piezoelectric overlayer for acoustic field generation. We study acoustic focusing in silicon-on-sapphire substrates with a scandium-doped aluminum nitride (ScAlN) piezoelectric overlayer, and outline the tradeoffs involved with efficient acoustic field generation into Sezawa modes, where the electromechanical coupling strength can be enhanced by increasing Sc%, and their injection and focusing into μm-scale silicon waveguides. In contrast to integrated photonics, strong confinement critically affects both generation and focusing efficiency, thereby imposing stronger constraints on material platforms that can provide a viable alternative to device suspension. We show that sapphire does not provide sufficient acoustic velocity contrast to silicon for shear waves, and a switch to higher contrast silicon carbide substrates is necessary to approximate the efficiencies that can be achieved in suspended devices.
Source: Applied Physics Letters
DOI: 10.1063/5.0334547
Institution: University of Bristol
Language: English
Subfield: Biomedical Engineering
Field: Engineering
Domain: Physical Sciences
Open Access status: hybrid
Awards: G1280652415, Stimulated Brillouin Scattering based RF to Optical Signal Transduction and Amplification, BrisSynBio: Bristol Centre for Synthetic Biology, G2072512383, Quantum Technology Capital: Quantum Photonic Integrated Circuits (QuPIC), G2218306764, Next generation Acoustic Wave Filter Platform, G3325982478, G3575769925, G396232211, G432395345, G4494338184, G4983140152, New directions in piezoelectric phononic integrated circuits: exploiting field confinement (SOUNDMASTER), G5133049693, G621933505, G6891521090, G7045001909, G7082644327, G7189482886, G8099952413, G8696683326, G926075884
OpenAlex ID: W7203631969