# Levitated cavity optomechanics in high vacuum

## TL;DR

This paper demonstrates dispersive coupling of a silica nanoparticle to a high-finesse optical cavity in high vacuum, achieving control over optomechanical interactions and paving the way toward strong cooperativity regimes.

## Contribution

It introduces a method for controlling and measuring optomechanical interactions of a levitated nanoparticle in high vacuum with detailed characterization.

## Key findings

- Achieved nanometer-level control of particle position within the cavity.
- Measured all relevant coupling rates and losses in the system.
- Obtained a quantum cooperativity of 0.01, close to the strong coupling regime.

## Abstract

We report dispersive coupling of an optically trapped silica nanoparticle ($143~$nm diameter) to the field of a driven Fabry-Perot cavity in high vacuum ($4.3\times 10^{-6}~$mbar). We demonstrate nanometer-level control in positioning the particle with respect to the intensity distribution of the cavity field, which allows access to linear, quadratic and tertiary optomechanical interactions in the resolved sideband regime. We determine all relevant coupling rates of the system, i.e. mechanical and optical losses as well as optomechanical interaction, and obtain a quantum cooperativity of $C_Q = 0.01$. Based on the presented performance the regime of strong cooperativity ($C_Q > 1$) is clearly within reach by further decreasing the mode volume of the cavity.