Acoustic Loss in Thin-Film Lithium Niobate: An Experimental Study

Abstract

This work reports an experimental study of acoustic loss in thin-film lithium niobate (LiNbO 3 ) using acoustic delay lines (ADLs). Unlike prior resonator-based quality factor ( Q) studies, this approach directly extracts the damping in thinfilm LiNbO 3, avoiding the influence of other intricate loss mechanisms, e.g., anchor loss and electrode-induced loss. Acoustic attenuation of fundamental symmetric (S0) and shear horizontal (SH0) waves are studied in suspended LiNbO 3 thin films of different thicknesses. The attenuation is significantly higher in thinner LiNbO 3 films, suggesting the LiNbO 3 crystal degradation during the microfabrication as the primary loss origin. Nevertheless, the extracted equivalent Q in thin-film LiNbO 3 is still higher than reported values, suggesting that anchor design and electrode quality remain the bottlenecks for higher Q. The proposed loss extraction framework is readily extendable to other acoustic thin-film structures.

Lithium Niobate Piezoelectric Actuator-Integrated Fiber Fabry-Pérot Tunable Filter with Ultrahigh Speed and Linearity

“…The magnitudes of the experimentally measured dynamic displacements are relatively small compared with the simulated values in Figure 1e. There are several possible reasons for this, including the dielectric loss in the LiNbO 3 and substrate material, 50 mechanical damping introduced by the adhesive layer, 51 and energy loss in the actuator due to airflow. 52 These can be optimized by changing the materials used in future studies.…”

RF acoustic microsystems based on suspended lithium niobate thin films: advances and outlook

“…anchor loss, electrical/mechanical loss in electrodes, and fabrication-induced deviations [121]. Recently, ADLs with unidirectional transducers have been extensively studied in thin-film LiNbO 3 [118] and provide great testbeds for measuring acoustic PL directly (figure 11). In operation, the EM signals are converted into acoustic vibrations at the input, unidirectionally propagating across the acoustic waveguide before converted back to EM waves at the output.…”