Phononic crystals for Love waves based on thin-film lithium niobate

This paper presents a type of surface acoustic wave (SAW) phononic crystals based on thin-film lithium niobate (LN). They are created by forming micro-pillar or micro-well structures on the LN, resulting in significant Rayleigh and Love SAW bandgaps. Especially for Love waves, they offer an irreplaceable advantage because they overcome the inability of conventional electrodes to reflect Love waves effectively. This enables the creation of high-quality, compact, high electromechanical coupling coefficient, stable and power-resistant acoustic resonators based on Love waves, potentially leading to a new generation of high-performance SAW filters and sensors. In this paper, we demonstrate the feasibility of such phononic crystals using xy-cut LN-on-SiC. However, it is worth noting that other piezoelectric materials such as lithium tantalate can also be used instead of LN, and high acoustic velocity substrates such as sapphire and diamond can be substituted for SiC.