Vertical-Reflection Multi-Pass Detection Method for Enhancing SERF Atomic Spin Measurement

SERF atomic co-magnetometer offers high sensitivity and navigation-grade potential. However, the performance of traditional single-pass detection methods is limited due to insufficient Faraday rotation signals. To address this issue, this paper proposes a vertical-reflection multi-pass detection method. By introducing hollow roof mirrors and half-wave plates, the optical interaction path is significantly extended while ensuring strict orthogonality between the pump and probe beams. This compact square shaped optical path design effectively amplifies the Faraday rotation effect, suppresses cross-axis coupling, and significantly improves the signal-to-noise ratio and measurement sensitivity. Through theoretical modeling analysis, this approach enhances the rotation signal while extending the optical path, thereby improving the system response. Experimental results demonstrate that the multi-pass structure improves the signal-to-noise ratio by several times compared to single-pass detection, and the design offers excellent integration potential, providing a feasible technical path for high-performance SERF quantum sensors for navigation and high-precision physical research.