Coherent Population Trapping (CPT) magnetometer empowering three-dimensional magnetic vector measurement based on dual-beam with lin//lin polarization

Abstract

Theoretically, all-optical Coherent population trapping (CPT) atomic magnetometers, which are based on the coherence effect of light and atoms, can achieve highly sensitive in-situ measurements of three-dimensional magnetic field vectors. However, current CPT atomic magnetometers have yet to demonstrate significant progress in terms of three-dimensional direction acquisition of the magnetic field and high angular sensitivity. In this paper, we propose a novel CPT magnetometer capable of three-dimensional magnetic vector measurement based on dual-beam with lin//lin polarization. Two linearly polarized beams with mutually orthogonal propagation directions are employed to configure the three-dimensional vectorial CPT magnetometer. The angular output of the magnetic field vectors of the proposed CPT magnetometer is then modeled and analyzed based on the relationship between three key vectors: the laser wavevector, polarization, magnetic field direction, and CPT magnetic resonance signal amplitude. This allows for the subsequent obtention of an analytical solution of the magnetic field angle. Furthermore, an analytical approach was employed to examine the dual-beam installation error, leading to the formulation of a corrective theoretical model for the magnetic field vector output of the dual-beam CPT magnetometer. The model’s validity was substantiated through experimental verification, thereby enhancing the precision of the system. The results experimentally demonstrate that the scalar sensitivity of the proposed CPT magnetometer is less than 5pT/Hz^1/2 at 1–10 Hz, and the optimal angular sensitivity achieves 0.01 deg/Hz^1/2 at 1–10 Hz, which is in accordance with the international precedent level. The proposed method will provide valuable support in the fields of cardio-magnetic measurement and prospecting.