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

Abstract

A new electrostatic actuator for a double layer deformable mirror 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 separate the parameters of actuation voltage, spring constant, and resonance. The feature reduces the complexity in the designing of a double layer deformable mirror with continuous phase sheet that are widely employed in the adaptive optics area of astronomy. The fabricated device has a diameter of 1250 µm with 4 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 approximately 5 µm displacement with a drive voltage of less than 30 V with an actuator-electrode separation of 15 µm, based on performance parameter found experimentally.