A compact micromachined interferometric accelerometer based on the diffraction grating

Abstract

In this paper, a MOEMS accelerometer with integrated-grating-based optical interference detection is presented. The acceleration sensor consists of an integrated grating on a transparent substrate and a mechanical part of a bulk silicon proof mass suspended by cantilevers attached to the silicon support substrate. The proof mass and cantilevers were fabricated with a two-mask process on one silicon-on-insulator (SOI) wafer. A phase sensitive diffractive grating was formed with the grating and the upper surface of the proof mass, which acts as a reflective mirror. Illuminating the grating with coherent light generates a series of diffracted optical beams, whose angles remain fixed, but whose intensities are modulated by the relative distance between the grating and the proof mass. Distance alteration caused by vibratory accelerations, changed the intensities of the diffracted beams, which could be detected by a differential circuit to get the variety of acceleration. Experimental results demonstrated that this MOEMS accelerometer has good performance with sensitivity of 3.63x10⁴V/g and a dynamic range of ±5g.