The theoretical mechanism for realizing a negative refractive index material in an optical frequency range with an atomic gas system of electromagnetically induced transparency (EIT) is studied. It is shown that under...The theoretical mechanism for realizing a negative refractive index material in an optical frequency range with an atomic gas system of electromagnetically induced transparency (EIT) is studied. It is shown that under certain conditions such a dense gas can exhibit simultaneously negative permittivity and negative permeability, and negligibly small loss.展开更多
Due to interaction with the vacuum of the radiation field,a K-type atomic system with near-degenerateexcited and ground levels,which is driven by two strong coherent fields and two weak probe fields,has additional coh...Due to interaction with the vacuum of the radiation field,a K-type atomic system with near-degenerateexcited and ground levels,which is driven by two strong coherent fields and two weak probe fields,has additional coherenceterms—the vacuum-induced coherence (VIC) terms.In this paper,we find that,if the interference is optimized,thetwo-photon absorption properties of this atom system can be significantly modified and electromagnetically-inducedtransparency (EIT) is dependent on this interference.Furthermore,we find that in all the cases the coherence can suppressor enhance the partial two-photon transparency,while the complete transparency window is still strictly preserved,whichmeans that it cannot be affected by the VIC.Another important result is the finding of the crucial role played by therelative phase between the probe and coupling fields:the relative height of absorption peaks can be modulated by therelative phase.The physical interpretation of the phenomena has been given.展开更多
We study the interaction of a weak probe field, having two circular polarized components, i.e., cr- and a＋ polarization, with an optically dense medium of four-level atoms in a double-A configuration, which is mediat...We study the interaction of a weak probe field, having two circular polarized components, i.e., cr- and a＋ polarization, with an optically dense medium of four-level atoms in a double-A configuration, which is mediated by the electromagnetically induced transparency with a polarized control light with spatially inhomogeneous profile. We analyse the deflection of the polarized probe light and we find that we can selectively determine which circular component will be deflected after the polarized probe light enters the atom medium via adjusting the polarization and detuning of the control field.展开更多
Based on the power dissipating model of spherical sample in free convection gas medium and the expression of input power, the model of temperature calculation for electromagnetic levitation melting sample was establis...Based on the power dissipating model of spherical sample in free convection gas medium and the expression of input power, the model of temperature calculation for electromagnetic levitation melting sample was established. Considering the limitation of levitation force and levitation sample temperature,the principle of stability levitation zone computation was determined. A spherical sample （ThDy）Fe2 under the protection of argon gas was examined, and the effect of radius of levitation sample and perturbation on the stable levitation zone was investigated. The results show that longitudinal perturbation and transverse perturbation can shorten the length of stable levitation zone and the range of levitation sample radius. By increasing the sample radius and weakening the perturbation the electromagnetic levitation melting stability of sample can be improved.展开更多
基金Project supported by the National Natural Science Foundation(NSF) of China (Nos. 90101024 and 60378037) and the NationalBasic Research Program (973) of China (No. 2004CB719805)
文摘The theoretical mechanism for realizing a negative refractive index material in an optical frequency range with an atomic gas system of electromagnetically induced transparency (EIT) is studied. It is shown that under certain conditions such a dense gas can exhibit simultaneously negative permittivity and negative permeability, and negligibly small loss.
基金National Natural Science Foundation of China under Grant Nos.90503088 and 10775100the Fund of Theoretical Nuclear Center of HIRFL of China
文摘Due to interaction with the vacuum of the radiation field,a K-type atomic system with near-degenerateexcited and ground levels,which is driven by two strong coherent fields and two weak probe fields,has additional coherenceterms—the vacuum-induced coherence (VIC) terms.In this paper,we find that,if the interference is optimized,thetwo-photon absorption properties of this atom system can be significantly modified and electromagnetically-inducedtransparency (EIT) is dependent on this interference.Furthermore,we find that in all the cases the coherence can suppressor enhance the partial two-photon transparency,while the complete transparency window is still strictly preserved,whichmeans that it cannot be affected by the VIC.Another important result is the finding of the crucial role played by therelative phase between the probe and coupling fields:the relative height of absorption peaks can be modulated by therelative phase.The physical interpretation of the phenomena has been given.
基金Supported by the National Fundamental Research Program under Grant No. 2007CB925204the National Natural Science Foundation under Grant Nos. 10947135 and 10775048+4 种基金the Opening Project of Key Laboratory of Low Dimensional Quantum Structures and Quantum Control (Hunan Normal University),Ministry of Education, under Grant No. QSQC0903the Scientific Research Fund of Hunan Provincial Education Department under Grant No. 09C062the Construct Program of the Key Discipline in Hunan Provincethe Construct Program of the Key discipline in Changsha University of Science and Technologythe Foundation of Changsha University of Science and Technology
文摘We study the interaction of a weak probe field, having two circular polarized components, i.e., cr- and a＋ polarization, with an optically dense medium of four-level atoms in a double-A configuration, which is mediated by the electromagnetically induced transparency with a polarized control light with spatially inhomogeneous profile. We analyse the deflection of the polarized probe light and we find that we can selectively determine which circular component will be deflected after the polarized probe light enters the atom medium via adjusting the polarization and detuning of the control field.
文摘Based on the power dissipating model of spherical sample in free convection gas medium and the expression of input power, the model of temperature calculation for electromagnetic levitation melting sample was established. Considering the limitation of levitation force and levitation sample temperature,the principle of stability levitation zone computation was determined. A spherical sample （ThDy）Fe2 under the protection of argon gas was examined, and the effect of radius of levitation sample and perturbation on the stable levitation zone was investigated. The results show that longitudinal perturbation and transverse perturbation can shorten the length of stable levitation zone and the range of levitation sample radius. By increasing the sample radius and weakening the perturbation the electromagnetic levitation melting stability of sample can be improved.
