Suppression of magnetic field gradient of atomic spin polarization based on systematic parameter analysis in K-Rb-21Ne comagnetometer

In atomic comagnetometers, non-uniform atomic spin polarization distribution caused by light absorption leads to an excessive equivalent magnetic field gradient (MFG) within the system, severely degrading its sensitivity. Whereas single-parameter tuning often fails to achieve a global optimum, and active compensation methods such as optical path optimization and gradient coils are limited by issues of volume and magnetic interference, this paper proposes a comprehensive suppression strategy for atomic spin polarization MFG based on systematic parameter analysis. First, a quantitative model for analyzing the polarization MFG was developed using the Bloch equation with an incorporated diffusion term. Subsequently, an in-situ MFG measurement method based on nuclear spin relaxation was proposed. Building upon this foundation, a closed-loop suppression method was developed via the coordinated adjustment of systematic parameters. Experimental results demonstrate that the polarization MFG decreased more than tenfold, the nuclear spin transverse relaxation rate was decreased by 33.10%, and consequently, the inertial measurement sensitivity under volume constraints reached 4.58×10−6 ∘[jls-end-space/]/s/Hz1/2[jls-end-space/]. By achieving effective suppression of the polarization gradient at its physical source without increasing hardware complexity, this method provides significant technical support for enhancing atomic spin coherence and broadening the application of comagnetometers in miniaturized systems.