Microelectromechanical flexure PZT actuated optical scanner: static and resonance behavior

An optical, mirror system has been built using MEMS techniques while employing lead zirconate titanate (PZT) thin films as strong piezoelectric material. The system consists of two parallel silicon cantilever beams, on which the PZT was deposited, which were arranged to project inward from a common frame. The beams were laterally offset over a distance appropriate to fit a mirror between them. One end of each beam is fixed to the frame, while the other end is attached to a sideways projected bar, directed to the other beam. To each sideways bar a connector, parallel to the original beam, pointing toward the frame, was attached. Between both connectors a mirror was attached. The application of voltage across the electrodes on top and below the PZT causes the beams to bend as a monomorph, and the mirror between the beams to rotate around an axis through its center. A variety of thicknesses have been chosen to fabricate these devices. The mirror angle at a given voltage is inversely proportional to the square of the beam thickness, while the bandwidth is proportional to the thickness. Beams with thickness of 5 mu m were used to achieve optical angles in static mode of up to 40 degrees using voltages up to 13 V In that case a bandwidth of around 700 Hz was observed. In resonance optical angles of 10 degrees with a driving voltage as low as 100 mV were achieved. For devices with 30 mu m thick beams, optical angles of up to 30 degrees were observed in resonance at 17.4 kHz at driving voltages of around 6 V. Due to the proprietary design a figure of merit which may be defined as a product of the resonance frequency and optical angle, is much higher than one of the other PZT scanners.