Researchers of the group of Prof. XUE Fei in High Magnetic Field Laboratory, Chinese Academy of Sciences (CHMFL), recently developed a new micro-lens fiber-optical interferometer scheme about detecting the motion of driven microwire cantilevers.

Common in nature, mechanical resonators are devices or systems that exhibit resonance or resonant behavior, that is, it naturally oscillates at some frequencies, called its resonant frequencies.

With the reduction in size, the resonators based on suspended nanoscale objects, such as monolayer semiconductors, graphene, and micro- and nanowires, have attracted considerable interest.

The sensing capabilities of micro- and nano resonators have been used with great success in recent advances of various fields like vectorial scanning force microcopy. It should be noted that distinguishing the vibration modes of the cantilever may help to further improve the sensitivity of force detection. The orientations of the flexural modes with respect to the incident optical axis are crucial parameters for a cantilevered resonator.

Previous methods have adopted complex experimental setups using quadrant photo detectors or have required simultaneous detection of two flexural modes of the cantilever.

The researchers in CHFML simulated the flexural vibrations mode using a commercial finite element analysis software (COMSOL) and experimentally determined the orientations of the flexural vibrational modes of two cantilevered microwires using a home-built interferometer without any prior knowledge or assumption about these resonators.

By combining the interference and scattering effects of light interacting with a cantilever—in other words, scattering in two dimensions—it is possible to extract the mode angle from the projections of thermally driven vibrational eigen modes onto two orthogonal reference axes.

This method can be used to study the flexural vibration modes of cantilevered microwires and characterize individual flexural modes with arbitrary orientations, which provides a new tool for detecting vectorial forces.

This work was supported by the National Key Research and Development Program of China, the National Natural Science Foundation of China, the Technological Development Grant of Hefei Science Center of Chinese Academy of Sciences, and the Major Program of Development Foundation of Hefei Center for Physical Science and Technology.