Abstract
Two types of micromachined Fabry-Perot interferometers have been developed to serve as adjustable read-out interferometers for an optical fiber strain sensor system. The fabricated micromirror serves as one reflective surface of the Fabry-Perot cavity, with the cleaved, coated end of the input optical fiber acting as the second surface. Electrostatic and thermal actuators allow adjustment of the cavity spacing. Due to the particular system requirements, the micromotors used to position the mirror must provide large displacements (over 50μm) with sub-micron positioning accuracy. Two different embodiments of the interferometer design, including integrated micromotors, have been achieved. The first design, fabricated using the Cronos MUMPs 2.5-layer polysilicon process, consists of a pop-up mirror mounted on a slider that is positioned in front of the fiber by an electrothermal stepper motor. The second design, fabricated using Deep Reactive Ion Etching (DRIE) of single crystal silicon, uses a bulk etched silicon mirror that is positioned in front of the fiber by an electrostatic comb drive. Design, fabrication, and characterization of the interferometers are discussed.