Dead‐Zone‐Free NMOR Atomic Magnetometer Based on Excitation of Dual‐Axis Magnetic Pulse

Nonlinear magneto‐optical rotation (NMOR) atomic magnetometer has extreme precision and sensitivity. However, atomic magnetometer suffers from the problem of dead zone that the sensitive signal decays to zero if the magnetic field is along some specific directions relative to the sensor. In this paper, a new scheme based on excitation of dual‐axis magnetic pulse is presented to eliminate the dead zone of NMOR atomic magnetometer. The magnetic field measurement is based on the mode of free induction decay (FID), which allows pumping and detecting stages to be separated without interference from magnetic pulse. The dead zone model is developed for NMOR atomic magnetometer from the mechanism of interaction between optical field and polarized atoms. To eliminate the dead zone of NMOR atomic magnetometer, the response model with dual‐axis magnetic pulse excitation is established by using the density matrix theory for bias magnetic field in arbitrary direction. Then the proposed method of suppressing the dead zone is examined in the experiment, which is in agreement with the developed model. The results show that the method can effectively eliminate the dead zone of NMOR atomic magnetometer, which is of great significance to measurement of magnetic field in complex magnetic environment with variable direction.