Suppression of spin-exchange relaxation in Bell-Bloom magnetometer

The atomic spin-exchange relaxation is the most important limitation of the sensitivity for the optically pump magnetometers operated on non-zero magnetic field environment. In this paper, a method with 2π magnetic field pulse modulation is proposed to suppress the spin-exchange relaxation by counteracting the Larmor precession effect caused by the external magnetic field, which allows being operated under non-zero magnetic field. This method applies an additional periodic 2π pulse magnetic field repeated with the Larmor precession frequency on the conventional Bell-Bloom magnetometer. The theoretical model of the Bell-Bloom magnetometer responding with 2π pulse magnetic field is established, and the suppression of the spin-exchange relaxation is demonstrated experimentally. This method reduces the spin-exchange relaxation by 91.4% and improves the magnetometer response by 74.0%, which is directly beneficial to the sensitivity of the atomic magnetometer applied in μT-scale magnetic field.