Loop-locked Coherent Population Trapping Magnetometer Based On A Fiber Electro-optic Modulator

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.