Thermalization properties at mK temperatures of a nanoscale optomechanical resonator with acoustic-bandgap shield

TL;DR

This study investigates the thermalization behavior of a nanoscale silicon optomechanical resonator at millikelvin temperatures, revealing its potential for quantum photon-phonon experiments due to its low thermal coupling.

Contribution

It provides the first detailed measurement of phonon occupancy and damping in a nanoscale optomechanical crystal at millikelvin temperatures, demonstrating its suitability for quantum experiments.

Findings

Mechanical resonance couples to a thermal bath at 270mK

Coupling rate of 400Hz with high mechanical quality factor

Optomechanical crystal remains functional at sub-kelvin temperatures

Abstract

Optical measurements of a nanoscale silicon optomechanical crystal cavity with a mechanical resonance frequency of 3.6GHz are performed at sub-kelvin temperatures. We infer optical-absorption-induced heating and damping of the mechanical resonator from measurements of phonon occupancy and motional sideband asymmetry. At the lowest probe power and lowest fridge temperature (10mK), the localized mechanical resonance is found to couple at a rate of 400Hz (Q=9x10^6) to a thermal bath of temperature 270mK. These measurements indicate that silicon optomechanical crystals cooled to millikelvin temperatures should be suitable for a variety of experiments involving coherent coupling between photons and phonons at the single quanta level.