High-sensitivity monitoring of micromechanical vibration using optical whispering gallery mode resonators

TL;DR

This paper demonstrates ultra-sensitive detection of micromechanical vibrations using optical whispering gallery mode resonators, achieving shot-noise limited displacement sensitivity and enabling detailed mode analysis.

Contribution

It introduces a highly sensitive optical transduction method for micromechanical vibrations using whispering gallery mode resonators, with novel detection capabilities and mode identification.

Findings

Achieved shot-noise limited displacement sensitivity of 10^(-19) m/Hz^{1/2}

Successfully identified mechanical modes using finite element modeling

Measured broadband displacement noise consistent with thermorefractive noise models

Abstract

The inherent coupling of optical and mechanical modes in high finesse optical microresonators provide a natural, highly sensitive transduction mechanism for micromechanical vibrations. Using homodyne and polarization spectroscopy techniques, we achieve shot-noise limited displacement sensitivities of 10^(-19) m Hz^(-1/2). In an unprecedented manner, this enables the detection and study of a variety of mechanical modes, which are identified as radial breathing, flexural and torsional modes using 3-dimensional finite element modelling. Furthermore, a broadband equivalent displacement noise is measured and found to agree well with models for thermorefractive noise in silica dielectric cavities. Implications for ground-state cooling, displacement sensing and Kerr squeezing are discussed.