Study Of Nonlinear Effect In Four-level Atomic System Based On Quantum Coherence

Quantum interference in quantum optics has been discussed extensively recently, many interesting phenomena have been observed due to quantum interference among multi-channels atomic systems. In this thesis, by means of quantum optics theory, we have intensively investigated the problem theoretically, and a series of meaningful results are obtained.Quantum interference breaks through the tradition bottleneck while leading into the superposition principle in quantum mechanics ,it makes important progress in field such as microelectronic manufacturing progress, mere electronic device, quantum information, quantum communication encryption, and light quantum computer, etc.The key points of this thesis are presented as follows:In the first chapter ,we overview the tendency of the effects of quantum interference.In the second chapter ,we make an analysis of relevant research approaches, tools foundation of the theory.In chapter three, using numerical simulation methods, the absorption and dispersion properties of probe field in a four-level atomic system with two driving fields are analyzed. The phenomenon of performance gain can be obtained by choosing appropriate parameters. Meanwhile, lasing without inversion can be realized explicitly in this closed system.In chapter four, we investigate the absorption and dispersion properties of a lamda-type four-level system driven by coherent fields. The result obtained by means of numerical method indicates that by adjusting the intensity of Rabi frequencies of the coherent field under the steady state condition, three, double or single electromagnetically induced transparency can be obtained in this system. Explanations of these phenomena are given by using the dressed states theory.In chapter five, using matrix theory, the absorption and dispersion properties of a Y-type four-level system driven by three coherent fields are investigated on the condition of effect spontaneously induced coherence. The result obtained by means of numerical method indicates that by adjusting the relative phase of the coherent field in the steady state, the dispersion (gain) and dispersion of the probe field can be significantly magnified and weakened periodically.In the last chapter , By the means of numerical method, the real parts of both relative dielectric permittivity and the relative magnetic permeability will be negative simultaneously under the condition of choosing appropriately parameters, so the left handedness effect is obtained. In a certain scope, by adjusting the intensity of Rabi frequencies of the coherent field in the steady state, the ranges of left handedness effect are changed correspondingly. Additionally, the properties of the negative refractive index are studied in detail.