Probe beam influence on spin polarization in spin-exchange relaxation-free co-magnetometers

Spin-exchange relaxation-free (SERF) co-magnetometers have promising applications in both inertial navigation and fundamental physics experiments. However, the fluctuation in the spin polarization caused by the probe beam has a non-negligible influence on the co-magnetometer signal. In this paper, a theoretical model containing three parameters of the probe beam is established by extending the coupled Bloch equation. Based on this model, the influence of probe power density on the transient and steady-state response of the SERF co-magnetometer is analyzed. According to the transient response model, a new measurement method for transverse optical pumping of the probe beam is proposed. Then, for the steady-state response model, a steady-state error suppression method is suggested by adjusting the degree of circular polarization of the probe beam. Eventually, the suppression method is used to refine the SERF co-magnetometer, achieving a suppression rate of 70.31% in transverse electron spin polarization fluctuations, thus improving the co-magnetometer to a stability of 0.0079(circle) h(-1). To our knowledge, this is better than what has been reported so far.