Design, Fabrication, Modeling, and Testing of a Surface-Micromachined Micromirror Device

The Flexure-Beam Micromirror Device (FBMD) is a phase-only piston-style spatial light modulator which can be used for phase adaptive optics applications. This paper presents a complete study of a new design of a square FBMD, from original design considerations through final device testing and verification of the developed model. The model relates the electrical and mechanical properties of the device by equating the electrostatic force of a parallel-plate capacitor with the counteracting spring force of the device’s support flexures. The capacitor solution is derived via the Schwartz-Christoffel transformation to account for non-ideal electric fields. This complete model describes the behavior of any piston-style device, given its design geometry and material properties. It includes operational parameters such as ambient temperature, electric field fringing effects, and mirror surface deformations. The micromirrors presented in this paper were commercially fabricated in a surface-micromachining process. A microscope-based laser interferometer was used to measure the mirror displacement and surface deformation as a function of drive voltage.