Achieving Submillimeter Spatial Resolution and Signal Enhancement in SERF Atomic Magnetometers

Miniaturized spin-exchange relaxation-free (SERF) atomic magnetometers (AMs) have demonstrated ultrahigh sensitivity, making them widely applicable in biomagnetism, magnetic anomaly detection, and fundamental physics research. Their spatial resolution is fundamentally constrained by the millimeter-scale cell, limiting further improvements. Existing solutions primarily rely on reducing the sensitive volume, either by decreasing the cell size or by partitioning the sensing region through detector arrays, where each subregion corresponds to a portion of the vapor cell. The former, however, raises the noise floor, while the latter suffers from signal attenuation. To overcome these limitations, we propose a novel flux-guiding concentrator (FGC) based on high-permeability soft magnetic materials, which consists of a flux-guiding section and a flux-amplifying section. Furthermore, we establish a signal amplification and spatial resolution analysis model that comprehensively accounts for magnetic flux leakage and air propagation losses. Compared with conventional models, our model not only supports optimization for more complex structures but also provides a quantitative calculation of the signal amplification factor and a qualitative evaluation of the factors influencing spatial resolution. Using this model, we optimize the structural parameters through an intelligent optimization algorithm and experimentally validate that the FGC enhances the spatial resolution of the SERF magnetometer to 210 µm while amplifying the signal by a factor of 3.4, independent of signal frequency. This study provides an effective approach to simultaneously improving spatial resolution and signal in SERF magnetometers, thereby expanding their potential for high-precision measurement applications.