Design and fabrication of electrostatically driven in-plane MEMS rotational mirror with electrostatic rotary encoder

In this paper, design and fabrication results of `in-plane' type MEMS mirror device driven by rotational electrostatic actuators with angle sensing ability are reported for the first time. This MEMS mirror realizes rotational motion of a vertical mirror mounted on the SOI actuator stage, which can deflect or switch the reflected light angle in parallel to the same chip surface. Since optical fibers and the vertical mirror can be aligned with guide structures or slits fabricated by the same photolithography step, precisely self-aligned micro optical bench system with light deflection function can be easily constructed. In addition, electrostatic rotary encoder is integrated with the rotational actuator for detection of the absolute rotational angle of the mirror stage. The rotational actuator device was fabricated successfully, and ±2.4° stage rotation was obtained at a 96V actuator drive voltage. Also, in-plane optical light deflection has been successfully demonstrated with the rotational mirror put on the actuator.