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 degrees 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. Motivation: Micro optical bench (MOB) technology is a promising approach to realize precise micro optical system for various applications. Micro optical components and optical fibers are mounted by the slits or guide structures formed on the same plane on a chip. High precision alignment of each optical component can be realized in MOB approach; however, relative positions and angles of light path are unchangeable in the optical system. In order to realize light switches or optical modules with variable light path length, 'in-plane' rotational micro deflection mirror component is required to vary the optical path in MOB surface. In this study, "in-plane" and electrostatically driven MEMS rotational mirror device with angle sensing ability has been proposed, fabricated, and evaluated for the MOB applications.