Extracting Acoustic Loss of High-Order Lamb Modes at Millimeter-Wave Using Acoustic Delay Lines

This paper reports the characterization of acoustic loss at millimeter-wave (mm-wave) in high-order bulk Lamb waves using acoustic delay lines (ADL). Using periodically poled piezoelectric film (P3F) lithium niobate (LiNbO3) ADL testbeds, the propagation loss, group velocity, and propagation acoustic quality factor (Q) in the piezoelectric thin-film are extracted up to 30 GHz. This work also demonstrates the viability of employing high-order Lamb modes for enabling the frequency scaling of acoustic devices without relying on ultra-thin piezoelectric films or fine lateral feature size. An acoustic resonator is demonstrated on the same film stack to provide comparison and further validate the findings of the study.