Description
High-sensitivity magnetometry enables applications ranging from magnetoencephalography and magnetic anomaly detection to geological surveying and searches for dark matter and other exotic particles. Though SQUIDs and SERF atomic magnetometers offer benchmark sensitivities, their dependence on cryogenics or near-zero-field operation limits deployability, prompting room-temperature alternatives such as NV centres and cavity optomechanical sensors. Optomechanical magnetometry has advanced substantially, with on-chip whispering-gallery-mode (WGM) microtoroid devices achieving the best reported sensitivities of 1.68 pT/√Hz (Hu/Li, 2024), and free-space gap-swing Fabry–Pérot cavities reaching 620 fT/√Hz (Xu/Liu, 2024).
We present a fibre bonded optomechanical magnetometer consisting of a high finesse Fabry-Perot cavity coupled to a magnetostrictive Galfenol puck. Applied magnetic fields strains the Galfenol transducer, driving the mechanical resonator and shifting the cavity resonance facilitating optical readout. We achieve sensitivities below 300 fT/√Hz, establishing this design as a scalable route towards ultrasensitive fibre-coupled, cryogen-free magnetometry toward applications of biomagnetic sensing, magnetic anomaly detection and through-the-earth communication.
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