Dual-Axis Optical Modulation Atomic Magnetometer With Tunable Sensitive Axes

Accurate magnetic source reconstruction critically depends on high-sensitivity multi-axis measurements. Given the superior sensitivity provided by the spin-exchange relaxation-free (SERF) regime, the development of high-sensitivity multi-axis atomic magnetometers (AMs) based on SERF is of paramount importance. However, most existing multi-axis AMs rely on multiple high-frequency modulated magnetic fields, increasing the spin-exchange relaxation and leading to the complex crosstalk between nearby magnetometers in array applications, thus limiting the measurement performance. In this study, we propose a method for magnetic field measurement with tunable sensitive axes, based on all-optical dual-axis measurements. This method adjusts the direction of atomic spin precession by applying a bias magnetic field. It allows for flexible switching between the transverse dual-axis and longitudinal axis as needed, without introducing complex multi-axis modulated magnetic fields. Experimental results demonstrate transverse dual-axis sensitivities are 3 fT/Hz<sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">1/2</sup> for the <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">x</i>-axis and 2 fT/Hz<sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">1/2</sup> for the <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">y</i>-axis, while the longitudinal sensitivity for the <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">z</i>-axis is 6 fT/Hz<sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">1/2</sup> after switching the sensitive axis. Our approach offers significant advantages over existing methods, particularly in eliminating crosstalk and mitigating spin-exchange relaxation introduced by multiple modulated magnetic fields. Additionally, the successful detection of simulated magnetocardiography signals demonstrates the practical potential of this method.