Two-Axis Gimbal-Less Electrothermal Micromirror for Large-Angle Circumferential Scanning

In this paper, we present the design, simulation, fabrication, and characterization of a two-axis gimbal-less micromirror optimized for large-angle circumferential scanning applications. The single-crystal silicon micromirror consists of novel folded bimorph electrothermal actuators, flexural springs, and a mirror plate coated with a high-reflective Cr/Au thin film. A modified silicon-on-insulator microelectromechanical system process has been applied on the micromirror fabrication. The single-wafer process is based on deep reactive ion etching in order to achieve high fill factor as well as small outline of the micromirror chip. A new mechanical design of bimorph actuators is developed to further increase the mechanical deflection. Both theoretical and experimental results demonstrate that the micromirror can provide a uniform mechanical deflection up to ~9deg with multichannel driving voltages of less than 2.3 V to any angle in full 360deg circumference.