An optical switch is fabricated using micro-electro-mechanical system (“MEMS”) techniques. A thin mirror is fabricated in the major plane of the substrate and rotates about an axis perpendicular to the major plane to move into and out of an optical beam path. The mirror surface is open for chemical polishing and deposition, resulting in a high-quality mirror. In one embodiment, the backside of the mirror is patterned with reinforcing ribs. In another embodiment, a two-sided mirror is fabricated.