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arXiv · 2409.09885

Accurate vector optically pumped magnetometer with microwave-driven Rabi frequency measurements

Christopher Kiehl·Thanmay S. Menon·Svenja Knappe·Tobias Thiele·Cindy A. Regal
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Abstract

Robust calibration of vector optically pumped magnetometers (OPMs) is a nontrivial task, but increasingly important for applications requiring high-accuracy such as magnetic navigation, geophysics research, and space exploration. Here, we showcase a vector OPM that utilizes Rabi oscillations driven between the hyperfine manifolds of $^{87}$Rb to measure the direction of a DC magnetic field against the polarization ellipse structure of a microwave field. By relying solely on atomic measurements -- free-induction decay (FID) signals and Rabi measurements across multiple atomic transitions -- this sensor can detect drift in the microwave vector reference and compensate for systematic shifts caused by off-resonant driving, nonlinear Zeeman (NLZ) effects, and buffer gas collisions. To facilitate dead-zone-free operation, we also introduce a novel Rabi measurement that utilizes dressed-state resonances that appear during simultaneous Larmor precession and Rabi driving (SPaR). These measurements, performed within a microfabricated vapor cell platform, achieve an average vector accuracy of 0.46 mrad and vector sensitivities down to 11 $μ$rad$/\sqrt{\text{Hz}}$ for geomagnetic field strengths near 50 $μ$T. This performance surpasses the challenging 1-degree (17 mrad) accuracy threshold of several contemporary OPM methods utilizing atomic vapors with an electromagnetic vector reference.

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Christopher Kiehl, Thanmay S. Menon, Svenja Knappe, Tobias Thiele, Cindy A. Regal. 2025-02-26. Accurate vector optically pumped magnetometer with microwave-driven Rabi frequency measurements. https://doi.org/10.1364/optica.542502

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