High-Fill-Factor Micromirror Array With Hidden Bimorph Actuators and Tip–Tilt-Piston Capability

This paper presents the design, fabrication, packaging, and characterization of a novel high-fill-factor micromirror array (MMA) actuated by electrothermal bimorphs. In this paper, 4 × 4 MMA devices with an 88% area fill factor at normal incidence, 1.5 mm × 1.5 mm subaperture size, and single-crystal-silicon-supported mirror plates have been fabricated based on a single silicon-on-insulator wafer, without additional bonding/transfer processes. The bimorph actuators are hidden underneath the mirror plates, which are also protected by silicon walls. The MMA devices can directly be surface mounted onto driving circuit chips or printed circuit boards after fabrication. The subapertures can generate large tip-tilt-piston scanning and can individually be addressed. Static characterizations of the packaged devices show that each subaperture can achieve a piston stroke of ~310 μm and optical deflection angles greater than ±25° in both the x- and y-axes, all at 8-V dc. The preliminary laser-steering optical-phased-array capability of the obtained MMA device has also experimentally been demonstrated. This paper is based on the conference proceedings presented at the 23rd IEEE International Conference on Micro Electro Mechanical Systems (MEMS 2010), Hong Kong.