Fundamental Antisymmetric Mode Acoustic Resonator in Periodically Poled Piezoelectric Film Lithium Niobate

TL;DR

This paper presents the design and fabrication of a novel antisymmetric mode RF acoustic resonator in periodically poled lithium niobate, achieving high quality and coupling factors suitable for miniaturized signal processing and sensing applications.

Contribution

It introduces the first efficient A0 mode resonator in P3F lithium niobate, leveraging periodic poling to enhance performance for small-scale devices.

Findings

Achieved a quality factor of 800 at 294 MHz

Demonstrated an electromechanical coupling of 3.29

Realized a figure of merit of 26.3

Abstract

Radio frequency (RF) acoustic resonators have long been used for signal processing and sensing. Devices that integrate acoustic resonators benefit from their slow phase velocity (vp), in the order of 3 to 10 km/s, which allows miniaturization of the device. Regarding the subject of small form factor, acoustic resonators that operate at the so-called fundamental antisymmetric mode (A0), feature even slower vp (1 to 3 km/s), which allows for smaller devices. This work reports the design and fabrication of A0 mode resonators leveraging the advantages of periodically poled piezoelectricity (P3F) lithium niobate, which includes a pair of piezoelectric layers with opposite polarizations to mitigate the charge cancellation arising from opposite stress of A0 in the top and bottom piezoelectric layers. The fabricated device shows a quality factor (Q) of 800 and an electromechanical coupling (k2) of 3.29, resulting in a high figure of merit (FoM, Q times k2) of 26.3 at the resonant frequency of 294 MHz, demonstrating the first efficient A0 device in P3F platforms. The proposed A0 platform could enable miniature signal processing, sensing, and ultrasound transducer applications upon optimization.