Decoupling and suppression of opto-thermal drifts in SERF atomic co-magnetometers via precise null-point characterization

The long-term bias stability of spin-exchange relaxation-free atomic co-magnetometers is significantly constrained by coupled opto-thermal fluctuations. Traditionally, random systemic offsets at the magnetic compensation point lead to inconsistent opto-thermal coupling, compromising the reproducibility of sensor performance. In this work, we propose a method to simultaneously decouple and suppress these primary drifts by precisely characterizing the physical null-point of the atomic ensemble. A combined compensation scheme, joining residual rotation angle alignment and transverse magnetic field adjustment, is implemented to isolate the sensor output from fluctuations in probe laser intensity and vapor cell temperature. Experimental results demonstrate that the sensitivities to temperature drifts and probe power fluctuations are suppressed simultaneously at the identified null-point by factors of 72 and 880, respectively. This approach establishes a stable zero point, which is expected to significantly enhance sensor reproducibility and stability without sacrificing fundamental sensing performance.