Optical Rotation of Levitated Spheres in High Vacuum

TL;DR

This paper demonstrates high-frequency optical rotation of microspheres in high vacuum, achieving MHz rotation rates with extremely low damping, enabling new precision measurement tools with levitated particles.

Contribution

It introduces the controlled optical rotation of microspheres in high vacuum at MHz frequencies, including non-birefringent materials, with unprecedented low damping times.

Findings

Rotation frequencies up to 6 MHz for birefringent spheres.

Damping time of 6×10^4 seconds for 10 μm SiO₂ sphere at 10⁻⁷ mbar.

No additional damping mechanisms beyond gas damping observed.

Abstract

A circularly polarized laser beam is used to levitate and control the rotation of microspheres in high vacuum. At low pressure, rotation frequencies as high as 6 MHz are observed for birefringent vaterite spheres, limited by centrifugal stresses. Due to the extremely low damping in high vacuum, controlled optical rotation of amorphous SiO$_2$ spheres is also observed at rates above several MHz. At $10^{-7}$ mbar, a damping time of $6\times10^4$ s is measured for a $10\ \mu$m diameter SiO$_2$ sphere. No additional damping mechanisms are observed above gas damping, indicating that even longer damping times may be possible with operation at lower pressure. The controlled optical rotation of microspheres at MHz frequencies with low damping, including for materials that are not intrinsically birefringent, provides a new tool for performing precision measurements using optically levitated systems.