Spatial Light Phase Modulator With Bidirectional Tilt–Piston Micromirror Array—Part I: Principle and Design

This paper proposes a novel structure of microelectromechanical-systems-based 1-D spatial light phase modulator (SLPM) that consists of a micromirror array on a silicon-on-insulator (SOI) wafer and indium tin oxide (ITO) electrodes on a glass plate. Each micromirror can exhibit bidirectional single-axis tilt, as well as up-and-down piston motions by combining the applied voltage on two ITO electrodes placed over the micromirror and the substrate of SOI (in the case that the substrate is energized, all micromirrors go down simultaneously). This device configuration enables SLPM to be fabricated by a simple process. Part I of this paper focuses on the principles and the design of the device. The optimum parameters of the device are derived to realize both tilt and piston motions, considering ways to reduce mirror warpage and crosstalk from the ITO electrode from the adjacent mirror. We simulate the dc and ac characteristics of the device and confirm that the designs that we optimized satisfy the target specifications to be widely used in optical communication systems.