Polarization-dependent center-of-mass motion of an optically levitated nanosphere

Abstract

In this study, we report the influence on the center-of-mass translational motion of a levitated nanosphere in the case of the combination of an elliptical polarization with an elliptical TEM00-mode Gaussian beam. A fundamental-mode Gaussian laser with a slightly elliptical profile is focused using a high numerical aperture objective lens for trapping a nanosphere. The field distribution of the strongly focused laser in the focus region depends on its polarization according to vector diffraction theory. Therefore, the motion of the nanosphere depends on the relative orientation and ellipticity of the two ellipses’ parameters. For a linearly polarized light field, the eigenfrequencies and corresponding power spectra of the radial motions change periodically with the rotation of the linear polarization direction relative to the orientation of the elliptical TEM00-mode Gaussian beam. We further demonstrate that these effects could be enhanced or canceled by controlling the relative orientation and ellipticity of the two ellipses’ parameters. This work provides a more flexible method for manipulating an optically levitated nanosphere. Furthermore, the above-mentioned effects can be used to evaluate a tightly focused laser using the motion of the nanosphere.