A bi-directional large-stroke electrothermal MEMS mirror with minimal thermal and temporal drift

This paper reports a novel bi-directional electrothermal MEMS mirror with its mirror plate's position insensitive to ambient temperature and stable over time. In contrast, the electrothermal MEMS mirrors demonstrated previously are unidirectional and the position of the mirror plate changes significantly with ambient temperature and drifts over time. The new MEMS mirror design has been fabricated and characterized. The bi-direction piston scan range reaches ±177 μm. The position of the released MEMS mirror plate is only 0.2 μm above the substrate surface, and changes merely 0.5 μm for a large ambient temperature change of 0–100°C. The temporal drift is just 0.7 μm over 600 hours. Both the thermal and temporal drift are reduced by nearly two orders of magnitude compared to previous unidirectional thermal bimorph MEMS mirrors.