MEMS mirrors based on a curved concentric electrothermal actuator

A curved concentric electrothermal actuator has been designed and developed to actuate circular micromirrors with improved area efficiency, while at the same time achieving large scan range at low voltage. This actuator consists of three curved concentric Aluminum/Tungsten bimorphs for fast thermal response and high responsivity, and two rigid frames connected in between for scan range amplification. A tip–tilt–piston micromirror with a circular mirror plate based on this actuator design has been proposed and fabricated. The mirror is capable of scanning ±11° at 0.6 V, and generating a 227 μm piston displacement at only 0.8 V. The measured lateral shift and tilt angle of the mirror plate are less than 7 μm and 0.7°, respectively, through the entire piston displacement. A piston-only micromirror has also been demonstrated, and it has even smaller lateral shift of less than 3 μm and tilt of less than 0.4° through the piston scan range. This mirror generates large vertical displacement of about 200 μm at only 0.9 V.