In this paper, a novel surface and bulk hybrid micromachining process for fabricating a 16×16 electrostatically-actuated MEMS-based optical switch is introduced. The fabrication enhances the capabilities of rotation type of micromirrors by enlarging their rotation angle to 90 degrees, which will provide a wide variety of possible mechanical designs for many optical applications such as scanners and filters, especially those requiring large angular adjustment. Furthermore, monolithic integration of fiber grooves and micromirrors are achieved by utilizing accurate photolithography and etching techniques. The fabricated 2-μm-thick polysilicon mirrors are able to rotate inward by 90 degrees to a vertical position when the applied voltage reaches the pull-in value of 208 V. Under the shortest optical path in the 16×16 switch array, the average and worst-case measurement values of fiber-mirror-fiber insertion loss are 2.27 dB and 2.48 dB, respectively. A fatigue test turns out to show that the micromirrors and torsion beams are quite durable to endure more than 1.368×102 billion cycle-tilting movement.

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