Hybrid electrostatic actuator for micromirror tilting

A novel hybrid electrostatic actuator made up of a planar plate drive and a vertical comb drive is developed for actuating torsional micromirror. The device consisting of the actuator and an into-plane tiltable mirror is fabricated in SOI substrate based on bulk-and-surface mixed silicon micromachining. As demonstrated by experiment, the novel actuator can drive the mirror to achieve large-range continuous tilting as well as spontaneous 90deg tilting induced by the pull-in effect in a voltage control fashion. The continuous tilting range of the micromirror is increased to about 46deg. Both theoretical modeling and experimental observations indicate that, accompanying the increase in the continuous tilting range, the yielding voltage increases. The device has also been used as a mirror switch in an optical system, and the optical insertion loss is measured to be -1.98 dB