The integration of GHz-frequency, high quality factor (Q), and electrically tunable acoustic resonators holds significant potential for advancing applications in quantum information technologies, microwave photonics, and reconfigurable RF systems. However, simultaneously achieving these three characteristics within a single, scalable platform remains a fundamental challenge. Here, we report the experimental demonstration of a GHz quasi-BIC resonator in a piezoelectric thin-film shear horizontal (SH) wave system, achieved through a structurally simple piezoelectric-metal phononic crystal (PnC) architecture on a LiNbO₃ thin film. This approach enables leaky Fabry-Perot coupling mode and localized trapping quasi-BIC mode. Without the need for deep etching or intricate patterning, we achieve a room-temperature quality factor of 6 10⁴ at ~1 GHz in ambient air, corresponding to an f Q product of 6 10^13 Hz at quasi-BIC mode. Furthermore, we demonstrate efficient electrical tunability via low-voltage (0. 6 V) electrothermal modulation of the PnC structure, enabling a reversible transition between trapped and transmission states and yielding a high-contrast amplitude modulation of 47. 75 dB. Our results establish a lithography-friendly, fabrication-tolerant platform for realizing tunable, high-Q acoustic resonators at GHz frequencies, overcoming longstanding barriers in phononic device engineering. This work opens new directions for scalable on-chip phononic circuits in quantum acoustics, reconfigurable RF systems, and signal processing applications.
Xu et al. (Fri,) studied this question.