Optical characterization of micro-electro-mechanical structures

In this paper, semiconductor laser feedback interferometry is applied to the characterization of vibrating mass microsensors, such as gyroscopes and accelerometers. Complete characterization of such devices with this technique includes the identification of the vibration modes and the measurement of the resonance curves of the different axes, the determination of resonance frequency, quality factor and the actuation efficiency as functions of different parameters such as pressure. In the case of a gyroscope, tuning of the driving and of the sensing axes can be also performed, as well as the measurement of the Coriolis force. Thanks to its very simple optical implementation, feedback interferometry provides a viable alternative to the standard electrical measurements, and is especially useful for the characterization of prototypes, for which a dedicated electronics circuit is not yet available.