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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基于液晶极化光栅的微型原子磁力计超紧凑高精度差分检测方法


使用碱蒸气（如铷）的原子磁力计 （AM） 是磁场测量中最灵敏的传感器之一。它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元件，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。在本研究中，液晶偏振光栅 （LCPG） 和液晶四分之一波板的组合用于 AM 中的差分检测，其磁场强度通过测量来自 LCPG 的两个衍射光束的强度来确定。实验结果表明，所制备的 LCPG 表现出 3,656 的圆极化消光比，平均衍射效率达到 99 %。此外，基于 LCPG 的差分检测方法可以实现 1.48 × 10−7 rad 的角度分辨率。随后，在 AM 中采用该方法，以实现 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%，并实现了两个衍射光束的同侧分布，从而避免了额外的垂直光路。检测光学元件的有效厚度减小到微米级，允许将来作为薄膜集成到微加工的蒸汽电池上。本研究为具有极高灵敏度的小型化增材制造提供了一种实用的解决方案。