Variable optical attenuator based on a vertical comb drive actuated MEMS micromirror

This letter presents the design, simulation, fabrication, and successful demonstration of a variable optical attenuator (VOA) based on a micromachined micromirror combined with an optical fiber collimator. The micromirror has a size of 500μm in diameter and a rotational resonance of 4.94kHz. The micromirror was actuated by vertical comb drive which was fabricated by bulk micromachining process on a silicon on insulator (SOI) wafer. The VOA operates at a low driving voltage of 4.4V corresponding to the rotation angle of 0.3°. The turn-on and turn-off response time of the VOA are 1.6ms and 2.74ms, respectively. Finally, the optical attenuation was measured and an optical attenuation as large as 40dB was obtained.