Abstract

We investigate the optomechanical coupling of a propagating light beam to a sub-wavelength sized nanoresonator. Our experiment consists in a silicon carbide nanowire, positioned at the waist of a strongly focused laser beam generated with high numerical aperture objectives. Using the transmitted light, collected on a quadrant photodiode through a second microscope objective, we measure with a large dynamics the thermal noise of the nanowire. The degeneracy within each longitudinal flexural mode family is generally lifted due to a deviation from the perfect cylindrical symmetry, leading to perpendicular eigenmodes which can be resolved for sufficiently large mechanical quality factors. Their orientations are experimentally determined, which permits using the nanowire as an ultrasensitive vectorial force sensor, thermal noise limited at the attonewton level.

© 2015 IEEE