An optical centrifuge for levitated nanoparticles

The optical centrifuge is an established tool in molecular physics for inducing controlled rotation of molecules through the transfer of angular momentum from an optical field. Here the polarization vector is rapidly rotated up to high angular velocities, which subsequently rotates molecules up to high angular frequencies. This technique has been instrumental in studying molecular structure and collision processes. Recently, there has been significant interest in controlling the rotational motion of nanorotors to study non-classical states in these macroscopic systems. We describe the creation of an optical centrifuge for nanorotors formed by anisotropic nanoparticles levitated within an optical tweezer. We present a classical description of this process and discuss optimal schemes for the acceleration of the linear polarization vector to well-defined rotational frequencies. We report on the experimental realization of the centrifuge enabled by a fast in-line polarization controller. This approach is also compared to rapid switching between linear and elliptically polarized fields. Finally, we describe future experiments to probe the quantum nature of rotation in these systems.