2 ng/√Hz-resolution optomechanical accelerometer employing a three-dimensional MEMS interferometer

A portable and high-resolution optomechanical accelerometer employing a deformable grating-based micro-electro-mechanical system (MEMS) interferometer is presented in this Letter. The movable reflective mirror of this interferometer is realized by a low-frequency vertical sensing structure with a three-dimensional (3D)-spring construction, which, to the best of our knowledge, is first proposed and fabricated in this work. All the components of the sensor are packaged in a metal case with a compact size of 4 cm×6 cm×3.15 cm. The micrometer-scale springs permit the device to have a high mechanical sensitivity of 893.23 µm/g and a resultant self-noise below 2 ng/H z from 2 to 7 Hz. Meanwhile, the measured voltage responsivity is as high as 15,874 V/g, demonstrating it is one of the most sensitive accelerometers reported to date.