A Digital/Analog Electrostatic Actuating Mechanism For Optical Applications

A digital/analog electrostatic actuating mechanism that can be applied for optical applications is presented. The mechanism is composed of electrostatic actuators with nails and clamped torsion beams. Based on the pull-in phenomena of electrostatics and the morph-shape bending of the actuators, the mechanism can be used to achieve digital/analog motions depending upon the applied voltage-range. Finite element model of the electrostatic actuator had been simulated to demonstrate the concept of actuation principle when the applied voltage is increased. Two functional micromirror devices were developed using Poly-MUMPs process to demonstrate the actuating abilities and its corresponding performances. Simulations and experimental results indicated that developed tilting micromirror could reach 2.5 ~ 4.2-degree digital tilting angle with 1-degree analog fine-tuning range. With fine-tuning function, the micromirror device is adaptive to the environmental drifts that could be applied for precise positioning in optical switching applications. The linear analog-tuning characteristic provides a solution for optical scanning applications. For the case of micromirror device that could achieve piston/rotation motions, the digital/analog mechanism is applied to realize optical phase/amplitude modulations. Experiments indicated that the micromirror could achieve 0.3 μm-displacement in piston and 0.8-degree angle in rotation.