Measurements on a micromachined silicon gyroscope by feedback interferometry

Feedback interferometry is a useful tool to characterize micromachined devices. We consider a silicon vibrating gyroscope, in which the angular rotation is transduced into the vibration amplitude of a small suspended mass. Measurements of the mass displacement at submicrometer resolution are reported on a 400×400 μm sensor, using an 800-nm 20-mW laser diode. The resonance curves of the device have been determined for different values of pressure and other parameters, which allows us to tune the resonance frequency and maximize the Q factor. Hysteresis and other nonlinear phenomena on specific samples also have been detected. The proposed method provides a direct inspection tool and represents a practical alternative to the standard electrical measurements