A research prototype was developed to demonstrate the possibility to measure very weak force fields applied on the vibrating extremity of a suspended nanowire.
The vibrations of the nanomechanical oscillator are measured using optical readout techniques and it is driven by means of the radiation pressure force of a second laser beam.
The nanowire is simultaneously driven at the resonance frequencies of its 2 transverse fundamental eigenmodes, and the 2 driven trajectories are recorded and analysed in 2D in order to determine the eigenmode orientations and its eigenfrequencies.
Measuring the variation of those 4 quantities in presence of an external force field, permits to completely determine the 4 components of the local force field gradients experienced by the nanowire.
In addition to the realization of the advanced prototype, the project permitted to develop novel readout protocols based on signal analysis in real time based on FPGA algorithms.
This permitted to achieve force field imaging in quasi real time, only limited by the oscillator’s damping rate (approx. 10 measures per second), with a sensitivity in the attoNewton range in 1second, 6 orders of magnitude larger than the best commercial Atomic Force Microscopes.
Those protocols were employed in particular to image the electrostatic force field above nanostructured samples, as well as determining the optical force field experienced by the nanowire once immersed in an optical microcavity.
