Resonant Torsional Micro-Actuators Using Thin-Film Lithium Niobate

This paper reports the first torsional micro-actuator using a lithium niobate (LiNbO
₃
, 36° Y-cut) thin film with a record-high figure of merit ( FoM=θopt·mirror dimension·frequency) of 1582 °·mm·kHz at a resonance frequency of 1.268 MHz. The large piezoelectric coefficients and high-quality factors of single crystal LiNbO
₃
have been exploited to enable high coupling torsional actuation. The fabricated actuator has a mirror size of 22x40 μm
²
, and quality factors of 547 and 1497 in air and vacuum respectively. Moreover, the optical angle can exceed 31
^°
(θopt = 4·θmech) in both air and vacuum, leading to an FoM surpassing state-of-the-art high-frequency scanners. Our demonstration has shown great potential for scanning micro-mirrors, and light detection and ranging systems (LIDAR) applications where frequency scalability, scanning angles, and footprint are the main challenges.