Acoustic Loss of GHz Higher-Order Lamb Waves in Thin-Film Lithium Niobate: A Comparative Study

This work reports a comparative study of acoustic loss between different Lamb waves at GHz in thin-film lithium niobate (LiNbO
₃
). The propagation loss (PL) of higher-order Lamb waves in thin-film LiNbO
₃
is studied for the first time using acoustic delay line (ADL) testbeds. The acoustic wave attenuation and quality factors (
$Q$
) of different Lamb waves are extracted, showing higher
$Q\text{s}$
for higher-order Lamb modes than fundamental modes in air and vacuum at room temperature. The extracted
$Q\text{s}$
are higher than those reported in thin-film LiNbO
₃
resonators, implying the electrode and anchor-induced loss as the dominant loss factors. The ADL-based loss analysis framework is readily extendable to acoustic damping study in other microwave acoustic platforms. [2021-0165]