Precision MEMS flexure mount for a Littman tunable external cavity laser

A tuning element has been constructed using micro-opto-electro-mechanical systems (MOEMS) technology for Littman configuration external cavity tunable lasers. The device is fabricated by deep reactive ion etching of bonded silicon-on-insulator, using a single layer of patterning to integrate a fixed grating and a mirror that is rotated about a virtual pivot by an electrostatic comb drive. The mirror is mounted on a compound flexure. To ensure mode-hop free tuning, the pivot point should lie at the intersection of the mirror and grating planes. Candidate elastic suspensions are compared, and a combination of a cantilever and a portal spring, is selected. Interferometric measurements of electromechanical performance show that the mirror is rotating about a suitable remote point. Preliminary data are given for a Littman external cavity laser operating with a fixed MOEMS structure.