Imaging Resonant MEMS with Ultra-Broad Spectral Vibrometry from 1000 Hz to 10 GHz

This paper reports on an optical imaging method, pulsed laser interferometry (PLI), for micromechanical vibrations from several kHz to 10 GHz while maintaining an unprecedented femtometer-amplitude noise floor spanning such a broad spectrum. We first describe the instrument with analytical modeling, and then demonstrate the PLI using representative MEMS resonators. Frequency response results are presented for three MEMS resonators, including a kHz comb-drive actuator, a MHz quartz plate, and a GHz piezoelectric transducer. In addition, the noise floor for each device is recorded with the excitation power gradually attenuated and the response levelling off to noise. The PLI vibrometry is thus shown to achieve a noise floor at 36.7 fm/ Hz up to gigahertz frequencies, an order of magnitude lower than the state-of-the-art at similar frequencies, facilitating measurement and analysis for ultra-broad spectral resonant MEMS devices.