An Optical Interferometry Based MEMS Accelerometer Applicable to Seismic-Grade Measurement

Abstract

Traditional seismometers and gravimeters normally have large volumes and entail high manufacturing costs. Aiming at the miniaturization of such geophysical instruments, a portable Micro-electro-mechanical Systems (MEMS) accelerometer applicable to seismic-grade measurements is fabricated and characterized in this work. This accelerometer is operating on the deformable grating-based MEMS interferometer, where a new MEMS out-of-plane sensing chip employing double layers of 10 &#x03BC;m-thickness spring is first proposed. The simulation results show that this geometry has a low natural frequency of 52.23 Hz and undergoes a low stress of 26.94 Mpa under the gravitational acceleration. The test of the fabricated prototype is implemented in a quiet environment for tracking the inherent micro seismic peaks of Earth. The evaluation results demonstrate that the fabricated prototype has achieved a voltage sensitivity of 510.6 V/g. Furthermore, the noise estimation indicates that the self-noise of this sensor has reached 20 ng/&#x221A;<i>Hz</i> from 0.3 Hz to 20 Hz, and a bias stability of 235.4 ng is obtainable at room temperature. Combined with the compact package size of 40.5 cm³, the proposed device exhibits a promising prospect in the seismic-grade applications.