A High-Fill-Factor Piezoelectric MEMS Mirror Based on Bow-Shaped Unimorph AlN Actuators

Piezoelectric MEMS micromirrors for light modulation and optical beam steering have been drawing extensive attention recently, but their applications are still limited due to low fill factor and low resonant frequency, especially when the well-established piezoelectric material–AlN is employed. This study proposes a bow-shaped unimorph piezoelectric actuator that can generate multidegree-of-freedom motion with high fill factor. Particularly, a tip-tilt-piston (TTP) piezoelectric micromirror made of such actuators is designed, fabricated, and characterized. The fill factor is as large as 73% with a mirror plate size of$1.0\times 1.0$mm. The measured resonant frequencies for the piston, tip, and tilt modes are 0.890, 1.747, and 1.781 kHz, respectively. The measured maximum piston stroke and tip or tilt angle reach$3.3~\mu $m and 14.4 mrad with high linearity under 24 Vpp. This bow-shaped actuator design provides a new direction for enhancing piezoelectric actuation efficiency and capability.