Tuning mechanism for a MEMS external cavity laser

Miniature external cavity lasers have been demonstrated using a semiconductor optical amplifier (SOA), collimator and piezoelectrically actuated blazed grating in the Littrow configuration. For mode-hop free tuning, the grating should rotate about a remote pivot. A suitable method of rotation has been demonstrated using an electrostatic MEMS actuator carrying an external mirror, for an external cavity laser in the alternative Littmann configuration. Here we demonstrate integration of the optical element, elastic suspension and drive for a MEMS external cavity laser in silicon. The design is based on a Littrow cavity, using a conventional HR/AR coated SOA, collimated by a ball lens and coupled to a lensed fibre. The MEMS part is formed by deep reactive ion etching and undercut of bonded silicon-on-insulator material. The movable components consist of a blazed grating, suspension and electrostatic drives. A simple cantilever cannot provide the deflection needed to mimic rotation about the pivot. Here we have used a novel compound flexure, consisting of a cantilever (which carries the grating) connected to a portal frame (attached to the substrate at the pivot).