Analysis and Suppression of Optical-Magnetic Misalignment in an Atomic Comagnetometer

Ultrasensitive atomic comagnetometers (ACMs) are invaluable tools for both inertial measurement and fundamental physics research. However, the misalignment between the pump light and the main magnetic field affects the polarization characteristics of nuclear spins of the noble gas atoms, making it a significant source of noise. In this article, an atomic magnetometer response model with the optical-magnetic misalignment error is established, and the mechanism of the influence of optical-magnetic misalignment on nuclear spin polarization is analyzed. An in situ evaluation method and a suppression method of optical-magnetic misalignment error are proposed, and their effectiveness is verified through experiments with varying pump light incidence directions. The experimental results indicate that after optical-magnetic alignment using the proposed method, the spin polarization of the coupled atomic ensemble is enhanced by 20.7%, and the longitudinal relaxation rate of the nuclear spin is reduced by 6.9%. Additionally, the amplitude-frequency response (AFR) of the x-axis magnetic field is reduced by 33.2% at 1 Hz and by 53.1% at frequencies below 0.002 Hz. This indicates an improvement in the transverse magnetic field error suppression capability of the ACMs.