DOI: 10.1002/adma.202312861 ISSN: 0935-9648

Monolithic Strong Coupling of Topological Surface Acoustic Wave Resonators on Lithium Niobate

Zi‐Dong Zhang, Si‐Yuan Yu, Haitan Xu, Ming‐Hui Lu, Yan‐Feng Chen
  • Mechanical Engineering
  • Mechanics of Materials
  • General Materials Science


Coherent phonon transfer via high‐quality factor (Q) mechanical resonator strong coupling has garnered significant interest. Yet, the practical applications of these strongly coupled resonator devices are largely constrained by their vulnerability to fabrication defects. In this study, we achieve topological strong coupling of gigahertz frequency surface acoustic wave (SAW) resonators with lithium niobate. The nanoscale grooves are etched onto the lithium niobate surface to establish robust SAW topological interface states (TISs). By constructing phononic crystal (PnC) heterostructures, we realize a strong coupling of two SAW TISs, achieving a maximum Rabi splitting of 22 MHz and frequency quality factor product fQm of ∼ 1.2 × 1013 Hz. This coupling can be tuned by adjusting geometric parameters and a distinct spectral anti‐crossing is experimentally observed. Furthermore, we demonstrate a dense wavelength division multiplexing device based on the coupling of multiple TISs. These findings open new avenues for the development of practical topological acoustic devices for on‐chip sensing, filtering, phonon entanglement, and beyond.

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