Modelling of cavity optomechanical magnetometers

TL;DR

This paper develops a predictive model for cavity optomechanical magnetometers, analyzing various geometries and material compositions to optimize sensitivity, achieving predictions close to experimental results and suggesting pathways for improved device design.

Contribution

The paper presents a general recipe for predicting the sensitivity of cavity optomechanical magnetometers and analyzes different geometries and materials for enhanced performance.

Findings

Predicted sensitivity of 180 pT/√Hz at 28 μm resolution.

Potential sensitivity improvement to 20 pT/√Hz with material adjustments.

Good agreement between predictions and experimental observations.

Abstract

Cavity optomechanical magnetic field sensors, constructed by coupling a magnetostrictive material to a micro-toroidal optical cavity, act as ultra-sensitive room temperature magnetometers with tens of micrometre size and broad bandwidth, combined with a simple operating scheme. Here, we develop a general recipe for predicting the field sensitivity of these devices. Several geometries are analysed, with a highest predicted sensitivity of 180~p$\textrm{T}/\sqrt{\textrm{Hz}}$ at 28~$\mu$m resolution limited by thermal noise in good agreement with previous experimental observations. Furthermore, by adjusting the composition of the magnetostrictive material and its annealing process, a sensitivity as good as 20~p$\textrm{T}/\sqrt{\textrm{Hz}}$ may be possible at the same resolution. This method paves a way for future design of magnetostrictive material based optomechanical magnetometers, possibly allowing both scalar and vectorial magnetometers.