A robust, fast electrothermal micromirror with symmetric bimorph actuators made of copper/tungsten

This paper reports a fast, robust electrothermal bimorph micromirror with a symmetric inverse-series-connected bimorph actuator. The actuator is made up of symmetric Cu-W bimorphs with high sensitivity and fast thermal response. A unique backside DRIE release process is developed to keep the mirror surface intact during release. The micromirror is able to perform both piston and tip-tilt motion. A maximum piston displacement of 169 μm is achieved with lateral shift less than 1.5 μm at the driving voltage of only 2.3 V. The maximum optical angle achieved is ±13° at 2.3 V. This mirror gives fast thermal response of less than 7.5 ms. The resonances of the piston and tip-tilt modes are 1.58 kHz and 2.74 kHz, respectively.