Bulk micro machined quasistatic torsional micro mirror
One dimensional torsional micro mirrors for laser steering applications have been developed and manufactured at Fraunhofer Institute of Photonic Microsystems. Several design variations with rectangular plates are available. The device can be operated in resonant mode and quasistatic mode as well. The device is fabricated out of a BSOI wafer and a second conductive silicon wafer. The structure is assembled by conductive adhesive bonding. Torsional springs connect the mirror plate to the mirror frame mechanically and electrically. Filled isolation trench structures separate volumes of different electrical potentials at the frame and at the deflective mirror respectively. Comb drive structures at both sides of the deflectable mirror and the part of frame located opposite increases capacitance at both mirror half sides. Applying a low level drive voltage between the combs, the mirror can be operated in resonant mode. The second silicon wafer is placed below the deflective mirror and is electrically at ground. Applying a electrical potential of higher level to one side of the deflectable mirror, the mirror can be driven quasistatic and resonant as well. While the drive voltage is applied to one side of the mirror, the comb drive structure of the opposite side can be used for capacitance based position read out.