Optical Levitation of Nanodiamonds by Doughnut Beams in Vacuum

TL;DR

This paper proposes a method to optically levitate nanodiamonds with reduced heating in vacuum by using composite particles and specific doughnut-shaped laser beams, enabling advanced spin-optomechanical systems.

Contribution

It introduces a novel trapping technique using composite nanodiamonds and optimized laser beams to minimize heating, facilitating high-vacuum spin-optomechanical applications.

Findings

Optimal laser beam configurations identified for stable trapping.

Composite particles reduce heating effects during trapping.

Feasibility demonstrated for high vacuum spin-optomechanics.

Abstract

Optically levitated nanodiamonds with nitrogen-vacancy centers promise a high-quality hybrid spin-optomechanical system. However, the trapped nanodiamond absorbs energy form laser beams and causes thermal damage in vacuum. We propose to solve the problem by trapping a composite particle (a nanodiamond core coated with a less absorptive silica shell) at the center of strongly focused doughnut-shaped laser beams. Systematical study on the trapping stability, heat absorption, and oscillation frequency concludes that the azimuthally polarized Gaussian beam and the linearly polarized Laguerre-Gaussian beam ${\rm LG}_{03}$ are the optimal choices. With our proposal, particles with strong absorption coefficients can be trapped without obvious heating and, thus, the spin-optomechanical system based on levitated nanodiamonds are made possible in high vacuum with the present experimental techniques.