Grating-Based Acceleration Sensors with Optical Interferometric Readout and Closed-Loop Control

We have developed an optically-read inertial sensor, where microfabricated diffractive optics are used to read the displacement of a macroscale proof mass. The measured noise floor of the sensor is 3 ng/√Hz from 0.1 Hz to 100 Hz. Feedback is implemented with a macroscale motor coil and rare earth magnets, achieving a dynamic range of 176 dB. This allows the sensor to target planetary seismic applications, with field expeditions completed in Alaska and Greenland. Optical models were developed to explore the optical design space, resulting in innovate stepped grating designs which will facilitate optoelectronic integration for microscale devices.