Dual-Axis Optical Modulation Atomic Magnetometer With Tunable Sensitive Axes

The accurate magnetic source reconstruction critically depends on high-sensitivity multiaxis measurements. Given the superior sensitivity provided by the spin-exchange relaxation-free (SERF) regime, the development of high-sensitivity multiaxis atomic magnetometers (AMs) based on SERF is of paramount importance. However, most existing multiaxis 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 multiaxis modulated magnetic fields. Experimental results demonstrate that transverse dual-axis sensitivities are 3 fT/Hz^1/2 for the x-axis and 2 fT/Hz^1/2 for the y-axis, while the longitudinal sensitivity for the z-axis is 6 fT/Hz^1/2 after switching the sensitive axis. Our approach offers significant advantages over the existing methods, particularly in eliminating crosstalk and mitigating spin-exchange relaxation introduced by multiple modulated magnetic fields. Additionally, the successful detection of simulated magnetocardiography (MCG) signals demonstrates the practical potential of this method.