An approach for achieving uniform temperature distribution on the bimorphs of electrothermal micromirrors

Bimorph-based electrothermal micromirrors can generate large lateral-shift-free (LSF) vertical displacement by employing electrothermal bimorph actuators with multiple segments of bimorphs. The vertical displacement of an LSF bimorph actuator is maximized when all the bimorph segments have equal temperature change. However, due to the distributed heat conduction and convection, the temperature changes on different bimorph segments are different. We report a new LSF bimorph actuator design with non-uniform width bimorph segments to achieve a uniform temperature distribution among multiple bimorph segments. A model is developed to optimize the new LSF bimorph design with three biomorph segments with the widths of 25 µm, 110 µm and 75 µm, which reaches the same average temperature of 316 K on the three bimorphs with incentive current of 5 mA and convection coefficient of 500 W/m²K.