Optical centrifuge for nanoparticles

TL;DR

This paper demonstrates the creation of an optical centrifuge capable of rapidly spinning levitated nanorotors to high rotational speeds, with potential applications in nanoscale manipulation and studies of rotational dynamics.

Contribution

It introduces a method to generate an optical centrifuge for nanorotors, establishing conditions for stable acceleration and providing initial experimental tools for rapid angular acceleration.

Findings

Nanorotors can be spun up to over 100 MHz rotational speed.

Stable acceleration depends on optical trap properties and nanoparticle anisotropy.

High rotational speeds are achievable in modest vacuum over microsecond timescales.

Abstract

We study the creation of an optical centrifuge for the controlled rotation of levitated nanorotors within an optical tweezer. The optical centrifuge is created by rapidly rotating the linear polarization of the tightly focused optical field used to form an optical trap. We show that nanorotors, formed by anisotropic nanoparticles levitated within the trap, can be accelerated to well-defined rotational rates in excess of 100 MHz over durations of hundreds of microseconds. The initial conditions required for stable acceleration, based on optical trap properties and the anisotropic susceptibility of the nanorotor are established, and confirmed by numerical simulations. We also present initial experiments that have developed tools for the rapid angular acceleration of the polarization vector of the linearly polarized beam that is required to create the centrifuge. We show that over the acceleration durations in the 100 $\upmu$s range, high rotational speeds could be achieved in modest vacuum.