A translation micromirror with large quasi-static displacement and high surface quality

Abstract

A large displacement with high surface quality translation micromirror is presented. The micromirror consists of a magnetic actuator and a mirror plate. The actuator and the mirror plate are fabricated separately using two processes and then bonded together. The actuator consists of a moving film which is a 20 µm thick nickel film fabricated by MetalMUMPs and a solenoid located underneath the moving film. The moving film is designed to curve up through the residual stress gradient in the nickel film and a curve-up mechanism which includes four trapezoidal plates and anchoring springs. The mirror plate is simply diced from a polished silicon wafer and coated with a metal thin film. The mirror plate is bonded onto the central ring of the moving film. A solenoid attracts the moving film along with the mirror plate downwards to realize translation. A quasi-static displacement of 123 µm is achieved at a driving current of 400 mA. A high mirror surface quality is realized, e.g. 15.6 m of curvature radius and 2 nm surface roughness.