Low-voltage electrostatic actuators for deformable mirrors for adaptive optics

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Zhou, Yu
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In this thesis, a micromachined electrostatic actuator is proposed for a deformable mirror system that is designed to achieve a decent stroke (~10 µm) with a reasonable resonant frequency (>1 kHz) and a controlling voltage smaller than 30 V, which is fully compatible with existing ICs. This is achieved by employing an Al / SU-8 phase sheet that is less stiff than a single crystal silicon phase sheet; a spiral electrostatic actuator that separates the stiffness, the resonant frequency, and the drive voltage at a certain displacement; and finally a novel tri-electrode topology of the electrostatic actuator that replaces the drive voltage of a conventional electrostatic actuator with a high static drive voltage and a low varying controlling voltage just a fraction of the conventional drive voltage. All three parts of the design were proven to be functional as desired via simulation. Both the polymer phase sheet and the spiral actuator design were fabricated, and shown a similar performance to the simulation. A prototype electrostatic actuator with tri-electrode topology was also fabricated and tested, demonstrating performance as desired.
Electrostatic actuation, MEMS, Adaptive Optics, Deformable mirror