| The thesis focused on the systematically theoretical study on some phenomena about atomic coherence and quantum interference. Quantum coherence and interference has become one of the important forward subjects in laser physics and quantum optics. Recent studies have shown a lot of quantum phenomena such as coherent population trapping, electromagnetically induced transparency, index enhancement without absorption, electromagnetically induced handedness, etc. These new effects have great potential for the control of the coherence properties of a medium, the production of high frequency lasers, the information storage and high precision measurements.This thesis is presented as eight sections according to the contents: Chapter 1 is an introduction of the research background and the research purpose of the thesis. Chapter 2 is a review on the semi-classical theory of light-matter interaction. The following six sections are the introductions of the author's work.In Chapter 3, the absorption-dispersion properties in a M- type five-level atomic system interacting with external fields system have been discussed. It is shown that changing the control fields can influence the absorption-dispersion properties regularly. The electromagnetically induced transparency (EIT) can be obtained if the parameters are taken appropriately. When control fields Rabi frequencies were decreased, the EIT windows would be narrow and slow-light would be realized.In Chapter 4, the quantum mechanics system of interacting between double∧type four-lever atoms and four light fields is studied, we investigates how to realize quantum effect manipulation under double cooperating drive light fields.In chapter 5, we report the effects of Vacuum-Induced Coherence in a laser-driven four-level atom consisting of three near-degenerate upper levels have an additional coherence term due to interaction with the vacuum of the radiation field. We show that such coherence preserves electromagnetically induced transparency and optical bi-stability phenomena. The dynamical behaviors of the population distribution via vacuum-Induced coherence was analyzed numerically too.In chapter 6, the system of inverted Y-type four-level atoms interacted with multi-mode light fields is investigated. Firstly, the absorption-dispersion properties of the medium are discussed. Then the left handedness of the medium under the mechanism of quantum interference is discussed.In chapter 7, the electromagnetically inductive left-handedness in a four-level atomic system associated with a pair of upper excited hyperfine levels has been investigated. We also discussed the properties of left-handedness with vacuum-induced coherence arising from the cross coupling spontaneous emission pathways.In chapter 8, a V-type four-level atomic system has been investigated for realizing left handedness. It is shown that the negative refractive index can be achieved not only in the condition of weaker probe field and stronger coupling field, but also in the condition which the probe field and the coupling field are in the same order. The negative refractive index band is enlarged in the situation of stronger probe field and left handedness is enhanced.At last, the summary of the paper is presented.This project is supported by the National Natural Science Foundation of China (Grant No. 10464002, No. 60278016, No.60768001)...
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