Large area molded silicon nitride micro mirrors

Large area molded torsional micromirrors have been fabricated from thin films of lowpressure chemical vapor deposition silicon nitride. Optical surfaces as large as 400 (mu)m in diameter with surface deviations less than 0.33 (mu) have been fabricated from 1.5-(mu)m-thick layers of silicon nitride. Surface flatness was achieved by molding latticed silicon nitride fins to the backside of the mirrors. Fins as deep as 28(mu)m were constructed by deep reactive ion etching bulk silicon to produce molds for the fins prior to silicon nitride deposition. Mirrors with fins were shown to be insensitive to temperature effects within the range of 50-120 C. An optical switch with insertion loss less than 2 dB was constructed with the mirrors, demonstrating their potential as switch elements in optical systems.