Response optimization of a three-axis sensitive SERF magnetometer for closed-loop operation

Abstract

Most triaxial-vectorial magnetic field measurements with Spin-Exchange Relaxation Free (SERF) atomic magnetometer (AM) are based on the quasi-steady-state solution of Bloch equation. However, the responding speed of these methods is greatly limited because the frequency of the modulation signal should be slow enough to ensure the validity of the quasi-steady-state solution. In our work, a new model to describe the response of the three-axis sensitive SERF AM with high modulation frequency is presented and verified. The response of alkali-atomic spin to high-frequency modulation field is further investigated by solving the Bloch equation in a modulation-frequency-dependence manner. This solution is well verified by our experiments and can offer a reference for the modulation frequencies selection. The result shows a potential to achieve a SERF AM operating in a geomagnetic field without heavy aluminum shielding when the modulation frequencies are selected properly.