Measuring the orientation of the flexural vibrations of a cantilevered microwire with a micro-lens fiber-optic interferometer

Optical interferometers are powerful tools for studying the flexural vibrations of nano- and micro-mechanical resonators. When a cantilevered microwire vibrates along a direction away from the optical axis, the interference signal may not be optimal for detecting its vibrations. In this work, we identify the optimal locations for detecting the vibrations of a cantilevered microwire using a micro-lens fiber-optic interferometer. We take both the interference effect and the scattering effect of the microwire into account. Using a home-built interferometer, we verify the analysis by measuring a cantilevered microwire driven in various directions with respect to the optical axis. Our results show that the optimal detecting location strongly depends on the orientation of the vibrations. Based on this observation, we inferred the orientations of the flexural vibrational modes of two cantilevered microwires. Our results may be useful in studying the flexural vibration modes of cantilevered microwires and their applications in detecting vectorial forces.