Suppressing Virtual Magnetic Field Noise and Enhancing Spin Coherence in Hybrid Optical Pumping Atomic Magnetometers

A hybrid optical pumping method employing a broad linewidth laser is proposed to enhance spin coherence and suppress virtual magnetic field noise in atomic magnetometers. The central frequency of broad linewidth laser is tuned to the resonance peak of the alkali-metal atoms D1 line. Its multiple frequency components suppress AC-Stark shift fluctuations caused by pumping laser frequency variations, thereby reducing virtual magnetic field noise. In addition, these components decrease the average optical absorption cross-section, improving the uniformity of atomic spin polarization, further enhancing spin coherence and extending transverse relaxation time. Experimental results show that, compared with narrow linewidth pumping, the proposed method suppresses virtual magnetic field noise by 17.95% to 34.50%, and increases the magnetometer response by 1.62% to 30.31% at 5 Hz. The optimal and average sensitivities are improved to 0.052 fT/Hz ^1/2 and 0.212 fT/Hz ^1/2 (1–20 Hz), corresponding to increases of 8.77% and 50.93%, respectively.