Compact and high-stability laser power stabilization system for atomic comagnetometer via polarization direction insensitive Pancharatnam-Berry phase grating

Quantum sensing technology holds important significance in the forefront of explorations in magnetic field measurement, physics research, and inertial navigation. In optically pumped atomic sensors, laser power stability is essential for maintaining high sensitivity and long-term measurement stability. A major source of power instability is the fluctuation of the polarization direction, which is converted into power noise by polarization-sensitive optical devices, such as polarization beam splitter (PBS). In this work, a compact and high-stability laser power stabilization system for atomic comagnetometers is proposed based on a polarization-direction-insensitive Pancharatnam-Berry phase grating (PDIG). By means of the proposed PDIG, polarization and power errors induced by fluctuations in the incident polarization direction are effectively suppressed, and the overall system stability is significantly improved. Experimental results show that, over a continuous 10 h operation period, the optical power stability is improved by 43.4% compared with that of the conventional PBS-based power-stabilization system. In addition, polarization conversion and beam splitting are integrated into a single device by the PDIG, so that the conventional PBS and quarter-wave plate are replaced, enabling a more compact optical configuration. Further experimental tests performed on a compact atomic comagnetometer incorporating the proposed PDIG-based stabilization scheme demonstrate that, under otherwise identical experimental conditions, the long-term stability is improved by 29.8% compared with the conventional system. A promising route is therefore provided toward highly stable and miniaturized atomic comagnetometer systems for frontier physics exploration and inertial navigation applications.