The spin-exchange relaxation-free (SERF) atomic magnetometers (AMs) exhibit ultrahigh sensitivity in ultraweak magnetic field measurement, but their narrow bandwidth constrains the scope of their applications. To increase the bandwidth, magnetic field closed-loop control technology has been introduced into AMs with demonstrated efficacy. However, previous research on closed-loop AMs resulted in signal distortion problems, primarily due to imprecise closed-loop models and control parameters selection without theoretical support. This problem is specifically characterized by the unexpected amplification or reduction of signals at certain frequencies, directly leading to the degradation of the frequency performance of the closed-loop AM, making it unsuitable for applications requiring full-bandwidth measurement. In this study, we proposed a performance-enhanced closed-loop SERF AM, maximizing the bandwidth while ensuring consistent performance across the entire bandwidth. An accurate closed-loop system model was first established. Subsequently, an optimal relationship between the control parameters was proposed according to the eigenvalues of the closed-loop system, and the particle swarm optimization (PSO) algorithm was introduced to determine the optimal control parameters. The improved closed-loop system was constructed in a triaxial SERF AM, achieving an average bandwidth of 410 Hz and a sensitivity of 10 fT/Hz
1/2in three axes, while ensuring consistent performance across the entire bandwidth. With the proposed method, the optimized control parameters can be obtained only by requiring the frequency response of the open-loop AM, which is convenient and useful for closed-loop AM applications.
The bandwidth and dynamic range of spin-exchange relaxation-free (SERF) atomic magnetometers (AMs) are effectively broadened by introducing magnetic field closed-loop control, rendering it a focal point in AM research. However, there is a deviation between the commonly used closed-loop AM model and the single-beam closed-loop AM experimentally constructed. In this study, we comprehensively analyzed each component in the actual system and proposed a closed-loop model of the single-beam SERF AM. The accuracy of the proposed model was varied through a comparative experiment with different control parameters. Based on comparative experiments, a tenfold reduction was verified in the mean square error of the proposed model compared with the commonly used closed-loop model. As an accurate model is essential for effective closed-loop control, the proposed closed-loop single-beam SERF AM model provides a theoretical foundation for the research and application of closed-loop AMs.