The Study Of The Response Of Coherent Media To Electromagnetic Fields Under Extreme Conditions

The study of the interaction of coherent media with light under different conditions is one of the most hot research topics in the field of quantum optics, which makes the micro-mechanism of the interaction between a system and an external electromagnetic field clearly and can be applied to solve practical problems. It is possible to obtain light under extreme conditions with the development of laser technology. For example, the ultra-intense and ul-trashort laser pulses might be generated already with the development of femtosecond laser technology. Thus there are many new phenomena when quantum systems interact with these few-cycle laser pulses, such as carrier-envelope phase effect. The nonlinear effects become more important with the increase of then intensity of electromagnetic.In this thesis, the response of coherent media to electromagnetic fields under extreme conditions is studied. The main contents are as follows:First, the possibility of ultra-fast population transfer via two few-cycle laser pulses is s-tudied. In order to solve it, a proper model is given firstly. Then the analytic solutions of population transfer is simulated based on the model. The result indicates that it is possible to transfer population from a populated level via an intermediate state to the target level driven by two few-cycle (more than two optical cycle) pulses. Meanwhile the processes of on-or far-off-resonance stimulated Raman scattering with sequential or simultaneous ultrashort pulses are investigated respectively. Such theoretical results will promote the research on the coherent control via ultrashort pulses. Moreover, our simulation shows that the signal of the CEP depen-dent effect can be enlarged when the width of few-cycle pulse less than two optical cycles or in some conditions.In chapter 4, the response of a two-level dipolar molecule system with laser fields is inves-tigated. A two-level model with nonzero diagonal dipole matrix elements is adopted to describe the population dynamics of a dipolar molecule driven by several kinds of external fields, such as monochromatic periodic, linear, parabolic and sech~2 forms. We present the corresponding exact solutions to these different physical models in terms of the confluent Heun equations. It should be noticed that the generalized rotating wave approximation is not used in our model and the analytical solutions derived here are valid in the whole parameter space.In the fifth Chapter, the impact of Kerr nonlinear effect on the optimal squeezing in s-ingle photon resonance fluorescence has been studied during the optimal squeezing via two-level atomic-state purification. The feasibility of squeezing of atomic resonance fluorescence is shown to be optimized by a properly designed environment, which can be realized by a quasi-resonant cavity, is theoretically discussed. The Kerr effect is further studied and con-firmed by numerical simulation. Meanwihle the fragility of squeezing against dephasing is not substantially reduced for Kerr effect. All these may be important for various applications.The study of the properties of the coherent media driven by different electromagnetic fields in extreme conditions is a fundamental research topic.The population transfer via two few-cycle laser pulses, the population dynamics of a dipolar molecule driven by strong fields, and the optimal squeezing in single photon resonance fluorescence affected by Kerr effect have been studied in this thesis. Since the parameters used here are all experimental parameters, we believe that our research results can be confirmed experimentally in corresponding systems. Our work can lead other related research and application opportunities and may result in a substantial impact on technology.