Design and experimental demonstration of an electrothermal micromirror with large optical aperture and wide scan angle

Electrothermal micromirrors are attractive for optical imaging and sensing due to their large scan range, large displacement, and low-voltage operation. However, simultaneously achieving a large reflection area and a wide scan angle remains challenging because of inherent structural trade-offs. In this work, an electrothermal micromirror with a footprint of 4.5 mm × 4.5 mm was designed, simulated, fabricated, and experimentally characterized. Multiple complete bimorph actuators were monolithically integrated into each driving arm to enhance the actuation moment while optimizing thermal capacitance and heat conduction. The fabricated device achieved a mirror plate of 2.5 mm × 2.5 mm with an optical scan angle of ±20.5° at only 5 VDC, corresponding to a fill factor of 30.9% and a field of view of 41°. A maximum vertical displacement of 270 μm was obtained at 4 VDC, and the resonant frequency was 248 Hz with rise and fall times of 13.9 ms and 14.0 ms, respectively. Comparative analyses based on micro plate dimension, field of view, resonant frequency, and static and dynamic figures of merit demonstrate competitive performance compared to previously reported counterparts, indicating strong potential for optical imaging and sensing applications.