title: In situ magnetic compensation for potassium spin-exchange relaxation-free magnetometer considering probe beam pumping effect.
abstract: A novel method to compensate the residual magnetic field for an atomic magnetometer consisting of two perpendicular beams of polarizations was demonstrated in this paper. The method can realize magnetic compensation in the case where the pumping rate of the probe beam cannot be ignored. In the experiment, the probe beam is always linearly polarized, whereas, the probe beam contains a residual circular component due to the imperfection of the polarizer, which leads to the pumping effect of the probe beam. A simulation of the probe beam's optical rotation and pumping rate was demonstrated. At the optimized points, the wavelength of the probe beam was optimized to achieve the largest optical rotation. Although, there is a small circular component in the linearly polarized probe beam, the pumping rate of the probe beam was non-negligible at the optimized wavelength which if ignored would lead to inaccuracies in the magnetic field compensation. Therefore, the dynamic equation of spin evolution was solved by considering the pumping effect of the probe beam. Based on the quasi-static solution, a novel magnetic compensation method was proposed, which contains two main steps: (1) the non-pumping compensation and (2) the sequence compensation with a very specific sequence. After these two main steps, a three-axis in situ magnetic compensation was achieved. The compensation method was suitable to design closed-loop spin-exchange relaxation-free magnetometer. By a combination of the magnetic compensation and the optimization, the magnetic field sensitivity was approximately 4 fT/Hz(1/2), which was mainly dominated by the noise of the magnetic shield.
authors.affiliation: School of Instrument Science and Opto-Electronics Engineering, Beihang University, Beijing 100191, China.
authors.forename: Jiancheng
authors.initials: J
authors.lastname: Fang
authors.affiliation: School of Instrument Science and Opto-Electronics Engineering, Beihang University, Beijing 100191, China.
authors.forename: Tao
authors.initials: T
authors.lastname: Wang
authors.affiliation: School of Instrument Science and Opto-Electronics Engineering, Beihang University, Beijing 100191, China.
authors.forename: Wei
authors.initials: W
authors.lastname: Quan
authors.affiliation: School of Instrument Science and Opto-Electronics Engineering, Beihang University, Beijing 100191, China.
authors.forename: Heng
authors.initials: H
authors.lastname: Yuan
authors.affiliation: School of Instrument Science and Engineering, Southeast University, Nanjing 210096, China.
authors.forename: Hong
authors.initials: H
authors.lastname: Zhang
authors.affiliation: School of Instrument Science and Opto-Electronics Engineering, Beihang University, Beijing 100191, China.
authors.forename: Yang
authors.initials: Y
authors.lastname: Li
authors.affiliation: School of Instrument Science and Engineering, Southeast University, Nanjing 210096, China.
authors.forename: Sheng
authors.initials: S
authors.lastname: Zou