Piezoelectric MEMS fast steering mirror with high reliability for free-space laser communication

This paper reports a highly reliable piezoelectric Micro Electro Mechanical System (MEMS) Fast Steering Mirror (FSM) with large optical aperture (10 mm), which utilizes two-level-construction comprising a mirror plate and a actuator hidden beneath the mirror plate, achieving a high resonant frequency (⪆900 Hz) and a large quasi-static scanning range (4 mrad). The leverage structure is adopted not only to amplify the quasi-static deflection angle, but also to achieve a high fill factor (⪆50%). Moreover, compliant flexural structures are optimized to balance the stress to strengthen mechanical robustness. AlScN piezoelectric film is used as actuating material for high piezoelectric coefficient, high linearity and long-term stability. Through experimental verifications, the mirror has been proven to have high mechanical and thermal robustness, namely, withstands mechanical vibration (14.34 g), shock (500g@2ms) and temperature cycling (-40° to 80°) without performance degradation. Meanwhile, the on/off at equal stress experiment further demonstrates the lifetime of the mirror to be more than 12.0E9 cycles.