In-situ magnetic field compensation for zero-field NMOR atomic magnetometer

Nonlinear magneto-optical rotation (NMOR) magnetometers are essential sensors for detecting weak magnetic field, particularly in near-zero magnetic field environment. However, the presence of residual magnetic field in magnetically shielded devices often damages the performance of zero-field NMOR atomic magnetometer. In this paper, considering the presence of the residual magnetic field, we develop the response model of zero-field NMOR atomic magnetometer and analyze the effect of triaxial residual magnetic fields on magnetometer. The theoretical model reveals that the zero-field NMOR atomic magnetometer has the property of single-axis vector with the light propagation as the sensitive direction of the magnetic field. Aiming at the adverse effect of residual magnetic field on NMOR atomic magnetometer, a triaxial in-situ residual magnetic field compensation method based on sinusoidal magnetic field modulation is proposed according to the model. Both theoretical and experimental results substantiate the efficiency of the approach to compensating for the residual magnetic field. The sensitivity of magnetic field measurement after compensation is 19 fT/Hz^1/2, reflecting a 56% improvement over the uncompensated case. The estimated resolution of magnetic compensation is superior to 3.2 pT along three axes. This method is of significance for the accurate detection of extremely weak magnetic field signal.