Investigation Of EIT And Transient Properties In Multi-Level Atoms And Nuclei

Atomic Coherence effect is the result of the interaction of atomic and electromagnetic fields, it is of great value to the research and application . In recent years, many of the hottest research topics in optics as electromagnetically induced transparency (EIT),coherent population trapping (CPT),lasing without inversion (LWI),Quantum-Optical Switch and group velocity slowed and so on, are caused by the interaction of atoms and the interaction field .This thesis introduces the interaction of the two-level atom and the three-level atom detailedly ; The theory of electromagnetically induced transparency (EIT) in a three-level system is expounded . And we also research Vacuum Induced Coherence (VIC) and the transient property in the interaction of a four-level atom. Using semi-classical theory and the quantum theory of the interaction of light with matter, we discuss the probability amplitude method, density matrix method and the theory of dressed state by the two-level atom system. In this thesis , we analyze that the detuning of the interaction of the single-mode field and the two-level atom is not zero, and find that the particle quantity of the excitation-state and ground-state transition ratios the pulsant frequency inversely.Electromagnetically induced transparency (EIT) is a unique photic transparency phenomena arose by the interaction of the electromagnetic field and the atom system. Since the past 20 years of the concepts and methods of the electromagnetically induced transparency, we have obtained great progress and development in both the theoretical and the experimental research. Presently, the experimental technology of the EIT has very comprehensive application in the condensation of the phase noise ,the enhancement of the isotope separation , LWI, the enhancement of the non-linear energy conversion efficiency and the dispeller and produce of the forbidden transition.This thesis expounds the transient properties of Electromagnetically induced transparency in aΛ-type three-level atom system. Firstly, the connection of the absorbability-scattering characteristic, coupling field and probing field detuning is studied detailedly in this system. We find that the frequency at which the absorption of the probing light is zero, it is always in the position of two-photon resonance. When the Rabi frequency in coupling field is larger than the decay rate between the two ground states, we discuss the influence of the Rabi frequency in coupling field and the Rabi frequency in the probing field to the absorption and scattering of the probing light in the situation of coupling field resonance. We find that, the extent of the electromagnetically induced transparency increases gradually as the Rabi frequency in coupling field increases and the position at which the absorption enhanced apex and the scattering is zero changes; As the Rabi frequency in the explored field increases, the extent of light transparency weakens and the absorbing characteristic enhances.We also discuss the VIC in aΛ-type three-level atom system and achieve the condition of presence of the VIC and then analyses the absorption characteristic in the explored field varies with the corresponding phasic angleΦin the probing and the coupling field and dipole moment angle. We find that when the vacuum influence exists, it is easy to actualize the gain without inversion and we can control the gain by the corresponding phasic angleΦbetween the tuning interacting field and the dipole moment angleθ. This is a new method. The probe absorption varies with the corresponding phasic angleΦwhen the probing detuning is some fixed value. We find that the probe absorption is a periodic function of the corresponding phasic angleΦ,its tuning periods is 2Ï€;when the probing detuning is different, the amplitude changes of the without inversion is different and the relative phase of the maximum of the gain without inversion is also different.We research the interaction of the N-type four-level system. Under the semi-classical theory, we deduce the orderliness of the nonlinear absorption of the exploration light as the time changes transiently by the probability amplitude method. At first, let the signal light close at initialized time, the three-level system is in the electromagnetically induced transparency, then we discuss the situation of the signal light open. When the signal light is open, the absorption of the four-level system about the nonlinear exploration light can engender the effect of the damped oscillations. The lasting time of the whole damping of oscillations ratios the decay rateΓ₃ of the third level inversely. The effect of the damped oscillations is due to the Rabi frequencyΩ_c in coupling field and the Rabi frequencyΩ_s in signal field. When the Rabi frequencyΩ_c in coupling field is fixed, the nonlinear absorption enhances as the signal light Rabi frequencyΩ_s becomes larger and the absorption coefficient becomes large too. Contrarily when the signal light Rabi frequencyΩ_s is fixed, the nonlinear absorption enhances as the coupling light Rabi frequencyΩ_c becomes litter, but the times of the damping of oscillations reduces obviously. When the coupling light Rabi frequency ? c achieve a minimum, the nonlinear absorption of the effect of damped oscillations disappears completely. This characteristic provide some theory for the manufacture of the photo-quantum switch.Lastly, we research EIT and the absorption characteristic for the nucleus multi-level system of the high- k isomer for the first time. Under the semi-classical theory, we analyses the absorbability-scattering characters in the probing field about the Rabi frequency in the probing field, the Rabi frequency in the control field, the detuning in the control field by density matrix equation. Because of the stability of the high- k isomer in experiment, we can better achieve EIT. When the Rabi frequency in the probing field is different, the absorbability-scattering characters in the probing field is different, the primary EIT window also different. This thesis has steering effects about realizing EIT of the nucleus system in the experiment and absorbability-scattering character in the probing field, and also can offer help about realizing the quanta yawp decrease in nucleus system and the enhance of the non-linear mixing efficiency.