MEMS mirrors based on curved concentric electrothermal actuators with very small lateral shift and tilt

We present a curved concentric electrothermal actuator design that has very mall lateral shift and tilting. The actuator is made up of folded curved Al/W bimorphs with fast thermal response and high sensitivity. Two MEMS mirror designs based on this actuator design have been fabricated. The first MEMS mirror is a tip-tilt-piston scanning mirror capable of scanning up to ± 11° at voltage less than 0.6 V, and generating up to 227 μm piston displacement at less than 0.8 V. Through the entire piston motion, the lateral shift and the tilt angle of the mirror plate are less than 7 μm and 0.7°, respectively. The second MEMS mirror is a piston scanning mirror with enhanced symmetry, and less than 3 μm lateral shift and less than 0.4° tilt through the entire piston scan range have been achieved. This mirror gives large vertical displacement of about 200 μm at only 0.9 V.