Suppression of the beam splitting fluctuation in laser power stabilization system for an atomic comagnetometer

This article investigates the beam splitting fluctuation (BSF) in the laser power stabilization system (LPSS) of an atomic comagnetometer operating in the spin-exchange relaxation-free (SERF) regime, which significantly degrades the stability of the atomic comagnetometer. Theoretical analysis indicates that, in traditional LPSS (T-LPSS), the splitting ratio fluctuates with changes in liquid crystal variable retarder (LCVR) phase retardation, waveplate fast axis, and ambient temperature, leading to a decrease in the stability of transmitted laser power A novel LPSS based on ring-structured photodetectors (R-LPSS) is proposed, which utilizes the spatial intensity distribution characteristics of the laser to realize the stabilization of laser power and suppression of BSF. Experimental results reveal that, under equivalent laser power disturbances and environmental temperature variations, the stability of transmitted laser power in R-LPSS surpasses that of T-LPSS. By implementing R-LPSS in the atomic comagnetometer, improvements have been achieved in the repeatability of scale factor, the repeatability of electron polarization rate, and long-term stability. Specifically, the long-term stability of the probe background has increased by 47%, while the long-term stability of the output signal has increased by 31%. In addition, the BSF suppression method proposed in this work has strong potential for miniaturization and can be extended to other optical measurement instruments.