【作者】 胡勇；

【导师】 冯焱颖；

【作者基本信息】 清华大学 ， 仪器科学与技术， 2014， 硕士

【摘要】 高精度磁场测量技术在许多领域都有着广泛的应用，在地质学、材料科学、导航、磁异常检测、生物医学和基础科学研究等领域都发挥着越来越重要的作用。磁力仪的种类繁多，根据其特性的不同，不同种类的磁力仪有着不同的应用。基于相干布居陷俘原理（Coherent Population Trapping, CPT）的原子磁力仪，因为其独特的性质在很多领域有着很好的应用潜力。该磁力仪因其绝对测量的方案且无需校准，在导航和空间磁测方向有着很好的前景；其全光结构且易于小型化的特性，让它可以避免探头内金属的影响，可以很好地应用于生物磁测量；作为标量磁力仪CPT磁力仪对测量方向不敏感，它还是地磁图绘制的合适候选。本文研制成功了一套基于光纤电光调制器的相干布居陷俘原子磁力仪。在本论文中，主要完成了以下几个方面的内容。论文叙述了光与原子的相互作用以及与相干布居陷俘相关的理论，并建立了CPT磁力仪的理论模型。本文详细介绍了碱金属原子的能级结构，并依此讲解了光与原子的相互作用和塞曼效应等基本原理，同时介绍了原子泡中的弛豫现象和抗弛豫手段。在此基础上，文章建立了CPT的理论模型并介绍了CPT磁力仪的设计思路。设计并实现了基于87Rb D2线的CPT磁力仪测量系统。利用光纤电光调制器（Fiber Electro-optic Modulator, FEOM）和从激光器的边带注入锁定技术获得了空间分离、光强独立可调的6.8GHz频差的相干光，观测到约1KHz的CPT共振信号，并完成了对外部磁场的闭环跟踪测量。测量结果与商用磁通门磁力仪的测量结果有很好的吻合度，其灵敏度在90Hz带宽处低于100pT/Hz。设计并实现了基于87Rb D1线的CPT磁力仪测量系统。对DL100激光器进行了稳频，直接利用FEOM出射光作为系统所需的双色共振光场，成功观测到40倍信噪比的500Hz左右的CPT共振信号，并完成对外磁场的跟踪测量。该系统在100Hz带宽内灵敏度均超过8pT/Hz，达到同类研究先进水平。利用87Rb D1线的CPT磁力仪测量系统，进行了一系列的相关实验的探索。这些实验包括对镀膜技术在CPT磁力仪中的应用探究，环形光泵浦对CPT信号的影响，非线性塞曼现象在强磁场中的应用以及对双共振实验的初步探究。更多还原

【Abstract】 Magnetometer is widely used and playing a more and more important role in manyfields like geology, material science, navigation, magnetic anomaly detection,biomedicine and basic scientific researches. Different magnetometers have their owncharacteristics which meet the requirements of different applications. Among all themagnetic sensors, the magnetometer based on the effect of CPT (Coherent PopulationTrapping) has potential in various applications for its distinctive properties. Based onquantum transitions, the method is absolute and such a system does not requirecalibration and this quality makes it promising for navigation and space measurement.Because of its all-optical structure, it can be miniaturized and can also avoid theinfluence brought about by the metallic parts in the sensors like other kinds ofmagnetometers and this could be useful in bioscience. In addition, the CPT split isinsensitive to the direction of the magnetic field and this property makes CPTmagnetometers quite suitable for geomagnetic mapping, especially when using multiplecells or mechanical rotation. CPT-based magnetometer systems, using a FiberElectro-optic Modulator, have been successfully set up. And in the thesis, severalaccomplishments have been introduced as following.The thesis firstly introduced some CPT related theories, and built the theoreticalmodel for the CPT based magnetometer. We introduced the energy level structure of theAlkali-Metal, and explained the interactions between photon and atoms, the ZeemanEffect, relaxation phenomenon and anti-relaxation methods in a vapor cell. Based on theprevious knowledge, we built the theoretical model of CPT and described the designthought of the magnetometer.The CPT magnetometer based on87Rb D2line was successfully built up. Wederived the space-separated and light-intensity-tunable coherent laser beams with a6.8GHz frequency difference using the sideband injection-locking of diode laserstechnique with a FEOM. A CPT resonance signal with1kHz linewidth was observedand the magnetometer system is locked to the ambient magnetic field. The measurementdata we have achieved is well matched with the data measured by a commercialfluxgate magnetometer and the sensitivity is better than100pT/Hz at90Hz. The CPT magnetometer based on87Rb D1line was also successfully built up. Westabilized the DL100diode laser with the DFDL method, and obtained the dichromaticlight field through a FEOM. The CPT resonance signal this time had a linewidth ofabout500Hz with a contrast of40. The magnetometer system has achieved a sensitivityof below8p T/Hz at below100Hz bandwidth, making our research in the first classin the world for CPT magnetometer.A series of related experiments on the D1line system have also been conducted,including the wall-coated cells’ applications in CPT magnetometers, ring-shaped pumplaser for a CPT system, the potential application of nonlinear Zeeman Effect inhigh-intensity magnetic field, and the exploration of double resonance CPTmagnetometers.更多还原