Focusing surface-acoustic-wave resonators on thin-film lithium niobate with transverse-mode suppression
Phys. Rev. Applied 26, 024087 – Published 31 August, 2026
DOI: https://doi.org/10.1103/5kq4-c6rr
Abstract
Surface-acoustic-wave (SAW) resonators are a promising platform for constructing hybrid quantum systems, where confined acoustic waves enable strong interactions with various physical systems. Focusing SAW resonators, which reduce mode volume while suppressing diffraction losses, have recently been investigated for applications in such hybrid systems. However, the resonator leads to additional transverse-mode resonances, which cause undesired responses. In this work, we develop focusing SAW resonators using a thin-film lithium niobate on sapphire. A film thinner than the SAW wavelength allows a highly confined acoustic-wave mode to be localized on the substrate surface. By using contoured electrodes following a two-dimensional Gaussian beam shape, we focus the SAW mode to near the diffraction limit and confirm this focusing via optical imaging. Furthermore, by engineering the spatial mode overlap of the interdigital transducer electrodes, we suppress the excitation of higher-order transverse modes.
