The tunneling ionization (TI) is the most dominated ionization process in the production of terahertz radiation by two femtosecond lasers, although its validity above the ionization threshold of some gases is uncertai...The tunneling ionization (TI) is the most dominated ionization process in the production of terahertz radiation by two femtosecond lasers, although its validity above the ionization threshold of some gases is uncertain. In the present research, we employ a 1D fluid code to simulate the efficiency of the produced terahertz radiation by two femtosecond laser beams in air plasma. Two ionization models in the context of the TI process which are the Ammosov-Delone-Krainov (ADK) for noble gases and its developed molecular ADK (MO-ADK) model for molecular gases are intrinsically used to conduct this study. The main target of the present research is to examine the validity of these models Above-Threshold-Ionization (ATI) of these gases. For this purpose, we simulated the ionization rate and the power spectrum of the produced radiation, in addition we numerically evaluated the efficiency of the produced radiation as function of the input beams intensity at particular energy fraction factor, relative phase and initial pulse duration of these beams. These calculations conducted for a selected noble gas at varying energy levels and a chosen molecular air plasma gas at different quantum numbers. Numerical results near and above the ionization threshold of the selected gases have clarified that the ADK and MO-ADK model are successful valid to study the efficiency of the produced THz radiation at low energy levels and small quantum numbers of the selected gases, meanwhile, with any further increase in the energy level and the quantum number values of these gases, both of the ADK and MO-ADK are failed to correctly analyze the efficiency process and estimate its fundamental parameters.展开更多
A linear delayed position feedback control is applied to control the erosion of safe basins in a Holmes-Duffing system. The conditions of fractal erosion of the safe basin of the controlled system on the basis that th...A linear delayed position feedback control is applied to control the erosion of safe basins in a Holmes-Duffing system. The conditions of fractal erosion of the safe basin of the controlled system on the basis that the range of time delay leading to good control is obtained by the Melnikov method. It is found that the increasing time delay can reduce the basin erosion under a weak and positive feedback g^in. Then the evolutions of safe basins with time delay are presented in detail by the fourth Runge-Kutta and Monte-Carlo methods, which shows that the safe basin of the controlled Holmes Dulling system can be expanded, and its fractal can be reduced by the increasing time delay. These results suggest that delayed position feedbacks can be used as a good approach to control the erosion of safe basins.展开更多
The quantum phase transition from the Mott insulator to the superfluid phases of the bosonic atoms trapped in an optical lattice, in which the on-site interaction carl be tuned by a Feshbach resonance, is investigated...The quantum phase transition from the Mott insulator to the superfluid phases of the bosonic atoms trapped in an optical lattice, in which the on-site interaction carl be tuned by a Feshbach resonance, is investigated by a variational approach within mean-field theory. We derive an extended Bos^Hubbard model to describe this ultracold atomic system. By theoretical calculation and analysis, the phase diagram is shown clearly, and we find an exciting and novel phenomenon that is the appearance of the Mort insulator-sea （MI-sea）. Meanwhile, the experimental feasibility of observing the MI-sea is discussed by analyzing the published data related to the Fashbaeh resonance at present. Finally, the potential application of the MI-sea for quantum information processing and quantum computation is also discussed in detail展开更多
文摘The tunneling ionization (TI) is the most dominated ionization process in the production of terahertz radiation by two femtosecond lasers, although its validity above the ionization threshold of some gases is uncertain. In the present research, we employ a 1D fluid code to simulate the efficiency of the produced terahertz radiation by two femtosecond laser beams in air plasma. Two ionization models in the context of the TI process which are the Ammosov-Delone-Krainov (ADK) for noble gases and its developed molecular ADK (MO-ADK) model for molecular gases are intrinsically used to conduct this study. The main target of the present research is to examine the validity of these models Above-Threshold-Ionization (ATI) of these gases. For this purpose, we simulated the ionization rate and the power spectrum of the produced radiation, in addition we numerically evaluated the efficiency of the produced radiation as function of the input beams intensity at particular energy fraction factor, relative phase and initial pulse duration of these beams. These calculations conducted for a selected noble gas at varying energy levels and a chosen molecular air plasma gas at different quantum numbers. Numerical results near and above the ionization threshold of the selected gases have clarified that the ADK and MO-ADK model are successful valid to study the efficiency of the produced THz radiation at low energy levels and small quantum numbers of the selected gases, meanwhile, with any further increase in the energy level and the quantum number values of these gases, both of the ADK and MO-ADK are failed to correctly analyze the efficiency process and estimate its fundamental parameters.
基金Supported by the National Natural Science Foundation of China under Grant No 10902071, Shanghai Municipal Education Commission under Grant No YYY08004, Shanghai Leading Academic Discipline Project under Grant No J51501, and Key Project of the National Natural Science Foundation of China under Grant No 11032009
文摘A linear delayed position feedback control is applied to control the erosion of safe basins in a Holmes-Duffing system. The conditions of fractal erosion of the safe basin of the controlled system on the basis that the range of time delay leading to good control is obtained by the Melnikov method. It is found that the increasing time delay can reduce the basin erosion under a weak and positive feedback g^in. Then the evolutions of safe basins with time delay are presented in detail by the fourth Runge-Kutta and Monte-Carlo methods, which shows that the safe basin of the controlled Holmes Dulling system can be expanded, and its fractal can be reduced by the increasing time delay. These results suggest that delayed position feedbacks can be used as a good approach to control the erosion of safe basins.
基金Supported by the National Basic Research Program of China under Grant No 2005CB724500, the National Natural Science Foundation of China under No 140874009, and the Open Research Found of State Key Laboratory of Precision Spectroscopy （East China Normal University）.
文摘The quantum phase transition from the Mott insulator to the superfluid phases of the bosonic atoms trapped in an optical lattice, in which the on-site interaction carl be tuned by a Feshbach resonance, is investigated by a variational approach within mean-field theory. We derive an extended Bos^Hubbard model to describe this ultracold atomic system. By theoretical calculation and analysis, the phase diagram is shown clearly, and we find an exciting and novel phenomenon that is the appearance of the Mort insulator-sea （MI-sea）. Meanwhile, the experimental feasibility of observing the MI-sea is discussed by analyzing the published data related to the Fashbaeh resonance at present. Finally, the potential application of the MI-sea for quantum information processing and quantum computation is also discussed in detail
