Abstract Hybrid spin-exchange optical pumping (hybrid SEOP) using multiple alkali-metal species is commonly employed to improve the spatial homogeneity of alkali spin polarization in atomic magnetometers and comagnetometers. We investigate the dependence of spin polarization and its spatial homogeneity on the alkali density ratio D r = [ Rb ] / [ Cs ] in Rb–Cs hybrid vapor cells. A series of cells with controlled D r were fabricated and characterized using absolute electron paramagnetic resonance polarimetry at multiple positions along the cell axis. The results show that the density ratio strongly influences both the magnitude and spatial uniformity of alkali polarization through the competition among optical pumping, spin exchange, and spin-destruction processes. An optimal density ratio is observed near D r ≈ 6.59 ± 0.47 , where the polarization reaches its maximum while maintaining high spatial homogeneity (end-to-end ratio ∼89% and RMS homogeneity > 95 % ). Under typical operating conditions, the optimal density ratio lies in the range D r ≈ 4 –10. These results clarify the role of the alkali density ratio in Rb–Cs hybrid SEOP and provide practical guidance for optimizing hybrid vapor cells used in precision atomic magnetometers and comagnetometers.Abstract Hybrid spin-exchange optical pumping (hybrid SEOP) using multiple alkali-metal species is commonly employed to improve the spatial homogeneity of alkali spin polarization in atomic magnetometers and comagnetometers. We investigate the dependence of spin polarization and its spatial homogeneity on the alkali density ratio D r = [ Rb ] / [ Cs ] in Rb–Cs hybrid vapor cells. A series of cells with controlled D r were fabricated and characterized using absolute electron paramagnetic resonance polarimetry at multiple positions along the cell axis. The results show that the density ratio strongly influences both the magnitude and spatial uniformity of alkali polarization through the competition among optical pumping, spin exchange, and spin-destruction processes. An optimal density ratio is observed near D r ≈ 6.59 ± 0.47 , where the polarization reaches its maximum while maintaining high spatial homogeneity (end-to-end ratio ∼89% and RMS homogeneity > 95 % ). Under typical operating conditions, the optimal density ratio lies in the range D r ≈ 4 –10. These results clarify the role of the alkali density ratio in Rb–Cs hybrid SEOP and provide practical guidance for optimizing hybrid vapor cells used in precision atomic magnetometers and comagnetometers.

Journal of Physics D Applied PhysicsApr 21, 20261 citation

Theoretical description of transverse measurements of polarization in optically-pumped Rb vapor cells

Joan Dreiling, D. Tupa, Eric B. Norrgard

Bulletin of the American Physical SocietyJun 5, 20120 citations

Influence of nuclear spin on the D

sub 2

optical pumping of alkali vapors