GHz Rotation of an Optically Trapped Nanoparticle in Vacuum

TL;DR

This paper demonstrates GHz rotation of an optically trapped nanoparticle in vacuum by transferring light's spin angular momentum, revealing high-frequency rotation and pressure-dependent dynamics.

Contribution

It presents the first observation of GHz rotation frequencies in optically trapped nanoparticles and explores their dependence on optical power and pressure.

Findings

Rotation frequencies exceed 1 GHz at low pressures

Rotation frequency scales linearly with trapping power

Rotation response time depends on pressure

Abstract

We report on rotating an optically trapped silica nanoparticle in vacuum by transferring spin angular momentum of light to the particle's mechanical angular momentum. At sufficiently low damping, realized at pressures below $10^{-5}$ mbar, we observe rotation frequencies of single 100 nm particles exceeding 1 GHz. We find that the steady-state rotation frequency scales linearly with the optical trapping power and inversely with pressure, consistent with theoretical considerations based on conservation of angular momentum. Rapidly changing the polarization of the trapping light allows us to extract the pressure-dependent response time of the particle's rotational degree of freedom.