Atomic magnetometers (AMs) that use alkali vapors, such as rubidium, are among the most sensitive sensors for magnetic field measurement. They commonly use polarization differential detection to mitigate common-mode noise. Nevertheless, traditional differential detection optics, including polarization beam splitters (PBS) and half-wave plates, are typically bulky and large, which restricts further reductions in sensor dimensions. In this study, a combination of liquid crystal polarization grating (LCPG) and liquid crystal quarter-wave plate is used for differential detection in AMs, with magnetic field strength determined by measuring the intensity of two diffracted beams from the LCPG. The experimental findings indicate that the fabricated LCPG exhibits a circularly polarized extinction ratio of 3,656 and achieves an average diffraction efficiency of 99 %. In addition, the differential detection method based on LCPG can achieve an angular resolution of 1.48 × 10−7 rad. Subsequently, the method is employed in an AM to achieve an average magnetic sensitivity of 13.8 fT/Hz1/2. Compared to the PBS-based differential detection method, this method enhances the magnetometer response coefficient by 13 % and achieves co-side distribution of the two diffracted beams, thereby avoiding the need for additional vertical optical paths. The effective thickness of the detection optics is reduced to the micrometer scale, allowing for future integration as thin films onto microfabricated vapor cells. This study offers a practical solution for miniaturized AMs with exceptionally high sensitivity.

中文翻译：

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基于液晶偏振光栅的微型原子磁力计超小型高精度差分检测方法


使用铷等碱金属蒸气的原子磁力计 (AM) 是磁场测量中最灵敏的传感器之一。他们通常使用偏振差分检测来减轻共模噪声。然而，传统的差分检测光学器件，包括偏振分束器 (PBS) 和半波片，通常体积庞大，这限制了传感器尺寸的进一步减小。在这项研究中，液晶偏振光栅（LCPG）和液晶四分之一波片的组合用于AM中的差分检测，通过测量来自LCPG的两束衍射光束的强度来确定磁场强度。实验结果表明，所制备的LCPG的圆偏振消光比为3,656，平均衍射效率为99%。此外，基于LCPG的差分检测方法可以实现1.48×10−7 rad的角分辨率。随后，将该方法应用于 AM 中，实现了 13.8 fT/Hz1/2 的平均磁灵敏度。与基于PBS的差分检测方法相比，该方法将磁力计响应系数提高了13%，并实现了两束衍射光束的同侧分布，从而避免了额外的垂直光路的需要。检测光学器件的有效厚度减小至微米级，从而允许未来作为薄膜集成到微制造的蒸汽电池上。这项研究为具有极高灵敏度的小型化 AM 提供了实用的解决方案。