# Low-Frequency Magnetic Sensing Using Magnetically Modulated Microcavity Resonant Mode

## TL;DR

A new magnetic sensing method uses a vibrating microcavity to detect low-frequency magnetic fields with high sensitivity.

## Contribution

A novel microcavity-based sensor extends the measurable frequency range of magnetic field detection.

## Key findings

- The sensor achieved 12.49 V/mT sensitivity at 0.5 Hz magnetic fields.
- The bias instability noise was measured at 16.71 nT.
- The method uses optical readout for microcavity resonant mode changes.

## Abstract

We propose a low-frequency magnetic sensing method using a magnetically modulated microcavity resonant mode. Our magnetically sensitive unit with periodically changing magnetic poles is formed by combining an AC excitation coil with a microcavity. The microcavity vibrates at the frequency of the AC amplitude-modulated signal and changes its resonant mode when the sensing unit interacts with a low-frequency magnetic field. Signal processing is performed on the resonant spectrum to obtain low-frequency magnetic signals. The results of the experiment show that the measured sensitivity to a 0.5 Hz magnetic field is 12.49 V/mT, and a bias instability noise of 16.71 nT is achieved. We have extended the measurable frequency range of the whispering gallery mode microcavity magnetometer and presented a development in microcavity magnetic sensing and optical readout.