Spiral spring electrostatic actuator for double-layer deformable mirror with continuous phase sheet

Abstract. A new electrostatic actuator for a double-layer deformable mirror (DM) with continuous phase sheet is presented. The electrostatic actuator employs an upper electrode consisting of multiple Archimedean spiral spring arms supporting a small mass central attachment point and is capable of separating the parameters of actuation voltage, spring constant, and resonance. The feature reduces the complexity in the designing of a double-layer DM with continuous phase sheet, which is widely employed in the adaptive optics area of astronomy. The fabricated device has a diameter of 1250  μm with four single-crystal silicon spiral arms each having a length of 6030  μm, thickness of 15  μm, and width of 30  μm. The actuator was simulated and tested to have a resonant frequency above 2600 Hz and was simulated to be capable of reaching ∼5-μm displacement with a drive voltage of <30  V with an actuator–electrode separation of 15  μm, based on the performance parameter found experimentally.