Fang Xiujie, Wei Kai, Zhai Yueyang, Zhao Tian, Chen Xu, Zhou Mingti, Liu Ying, Ma Danyue, Xiao Zhisong
Opt Express. 2022 Jan 31;30(3):3926-3940. doi: 10.1364/OE.447041.
The magnetic field gradient within optical pumping magnetometers (OPMs) suppresses sensitivity improvement. We investigated the effects of the magnetic field gradient along the x-, y-, and z-axes on the limiting factors of magnetometers under extremely low magnetic field conditions. We modified the magnetic field gradient relaxation model such that it can be applied to atoms in the spin exchange relaxation free (SERF) regime. The gradient relaxation time and spin polarizations, combined with fast spin-exchange interaction, were determined simultaneously using the oscillating cosine magnetic field excitation and amplitude spectrum analysis method. During the experiments, we eliminated the errors caused by the temperature and pumping power, and considered different isotope spin exchange collisions in naturally abundant Rb during the data analysis to improve the fitting accuracy. The experimental results agreed well with those of theoretical calculations and confirmed the accuracy of the improved model. The contribution of the transverse magnetic field gradient to the relaxation of the magnetic field gradient cannot be ignored in the case of small static magnetic fields. Our study provides a theoretical and experimental basis for eliminating magnetic gradient relaxation in atomic sensors in the SERF region.
光泵磁力仪（OPM）内的磁场梯度会抑制灵敏度的提高。我们研究了在极低磁场条件下，沿x、y和z轴的磁场梯度对磁力仪限制因素的影响。我们修改了磁场梯度弛豫模型，使其能够应用于自旋交换无弛豫（SERF） regime中的原子。利用振荡余弦磁场激发和幅度谱分析方法，同时确定了梯度弛豫时间和自旋极化，并结合快速自旋交换相互作用。在实验过程中，我们消除了温度和泵浦功率引起的误差，并在数据分析过程中考虑了天然丰度铷中不同同位素的自旋交换碰撞，以提高拟合精度。实验结果与理论计算结果吻合良好，证实了改进模型的准确性。在小静态磁场情况下，横向磁场梯度对磁场梯度弛豫的贡献不可忽略。我们的研究为消除SERF区域原子传感器中的磁梯度弛豫提供了理论和实验基础。
