Factor Analysis Of The Signals Which Affect CPT Magnetic Field Detection

Magnetometry is an important method which is used to study physical magnetic phenomena. The technology of the weak magnetic field measurement plays an important role in scientific research, national defense, industry, bio-medical sciences, and daily life area. At present, there are several kinds of magnetometers whose applications are limited or inhibited because of their large weight and volume, power consumption or low resolution. Coherent population trapping (CPT) magnetometer which we will discuss in this thesis enjoys many advantages, including higher resolution, smaller size and lower power consumption. That’s why it has been paid more and more attentions from the scientists all over the world.In this thesis, many properties of a CPT magnetometer is investigated, including generalized principles, experimental setup, analyses of experimental results and the methods of experimental optimization.In Chapter 1, we introduce the importance of the weak magnetic field measurement and its application. First of all, the difference between the concept of sensitivity and resolution is presented. Secondly, we provide the operating principles and characters of commonly used high-sensitivity magnetometers. Thirdly, we analyze the advancing trend of magnetometers, requirement in various areas, and the significance of developing high-sensitivity magnetometers all by ourselves. At last, an introduction to the main contents of this thesis and its significance are given.In Chapter 2, through the basic theory on the interaction between atoms and electromagnetic field, we theoretically interpret the fundamental operating principle of CPT atomic magnetometers, including the character of Rb atom and Zeeman effect. Subsequently, we conclude the application direction of the CPT effect. Then, an introduction to the optical path diagram, experimental setup and elementary results are presented.In Chapter 3, in order to understand a better method of improving the sensitivity of magnetometers, we do the experiments in various aspects, including the effect of beam diameter, laser intensity, frequency detuning, laser polarization direction and sweep time on signal, laser polarization on magnetic field direction, cell temperature on signal, laser power stabilization on signal, phase locking of two lasers, buffer gas, stabilization of laser frequency and the performance of the detector. From the above experimental results, we directly observe various factors effecting line width of CPT signal. In addition, we make a theoretical derivation of part of the factors among them, as well as analogy calculation and qualitative interpretation. Finally an improving method is proposed.In Chapter 4, the main results of the thesis are summarized and an outlook is given about the broaden application prospects of CPT atomic magnetometers.