Sensitivity-Enhanced Dual-Axis Zero-Field Atomic Magnetometer Based on Pulsed Magnetic Field Modulation

Atomic magnetometers serve as a type of quantum sensing instrument, offering extensive applications in the field of extremely weak magnetic field measurement. Miniaturized zero-field atomic magnetometers typically use continuous high-frequency magnetic fields to modulate atomic spin precession for multi-axis measurements. However, this modulation induces additional spin-exchange relaxation, which significantly broadens the resonance linewidth. In this study, the pulsed magnetic field modulation is introduced instead of continuous modulation to reduce the effective duration of the magnetic field. This operation significantly diminishes perturbations of steady-state spin distribution in Zeeman sublevels caused by Larmor precession during each modulation cycle, thus effectively mitigating decoherence effects. The relationship between spin-exchange relaxation rate and pulsed field parameters is studied based on the generalized hyperfine Bloch equation, and a spin dynamics model under the pulsed modulation is developed. Agreement between experimental and theoretical results validates the suppression effect of spin-exchange relaxation and the accuracy of this model. Experimental results indicate that the pulsed modulation scheme results in a 30% reduction in the spin-exchange relaxation rate and achieves dual-axis sensitivities of 1.5 and 2.5 fT Hz^−1/2, respectively, representing improvements of 25% and 20% over conventional continuous modulation methods.