Optomechanics and thermometry of cryogenic silica microresonators

TL;DR

This paper reports on cryogenically cooled silica microresonators with high quality factors, demonstrating their potential for quantum measurements by analyzing their optomechanical properties and thermal behavior at millikelvin temperatures.

Contribution

It provides the first detailed thermometry and characterization of cryogenic silica bottle resonators, highlighting their suitability for quantum optomechanics.

Findings

Mechanical modes show laser-induced heating limiting phonon occupation to ~1500.

Thermalization to 9 mK bath could enable quantum ground state preparation.

High optical and mechanical quality factors observed at cryogenic temperatures.

Abstract

We present measurements of silica optomechanical resonators, known as bottle resonators, passively cooled in a cryogenic environment. These devices possess a suite of properties that make them advantageous for preparation and measurement in the mechanical ground state, including high mechanical frequency, high optical and mechanical quality factors, and optomechanical sideband resolution. Performing thermometry of the mechanical motion, we find that the optical and mechanical modes demonstrate quantitatively similar laser-induced heating, limiting the lowest average phonon occupation observed to just ~1500. Thermalization to the 9 mK thermal bath would facilitate quantum measurements on these promising nanogram-scale mechanical resonators.