Investigations Of Multi-level Electromagnetically Induced Transparency And Autler-townes Splitting Based On The Decaying-dressed-state Method

As a significant branch of optics,quantum optics developed in the 1960 s use modern quantum theory to study intriguing phenomena in the area of light-matter interaction.At present,laser-driven atomic system is one of the excellent platforms in quantum optics and atomic coherence induced by laser leads to numerous quantum optical phenomena,such as electromagnetically induced transparency,coherent population trapping,adiabatic population transfer,lasers without population inversion,laser cooling and trapping.And electromagnetically induced transparency(EIT)is a central issue in this thesis.Since its theoretical prediction and then experimental demonstration in the 1990 s,EIT has attracted a great deal of attention from quantum physicists and has been extensively investigated in various quantum systems.Beyond an interesting optical phenomenon itself,it also is a useful tool to manipulate the atom-field interaction at the level of quantum mechanics,which has obtained great applications in quantum nonlinear optics and quantum information science,such as nonlinear multi-wave mixing,giant Kerr nonlinearity,quantum information storage and readout,and alloptical switch.However,in contrast to EIT,there is a similar but distinct phenomenon,i.e.,Autler-Townes splitting(ATS).Because EIT and ATS have different physical origins,occur in the different parametric conditions,and bring about confusions in some previous literatures,to distinguish ATS from EIT is a significant issue.Focusing on this subject,we study EIT and ATS in a laser-driven five-level atomic system.In chapter one,we briefly introduce the concepts,research progresses,some applications of EIT and ATS.In chapter two,we utilize Schr?dinger equation and density matrix equation to calculate optical susceptibility in a three-level system.In chapter three,based on the decaying-dressed-state method,we present the physical conditions for distinguishing ATS from EIT.By decomposing the first-order probe response into two Lorentzians,we clearly show the different physical mechanisms for resulting in EIT and ATS.In chapter four,we present a detailed study of EIT and ATS in a five-level atomic system resolved into a four-level Y-type subsystem and a three-level ?-type subsystem.Using the standard density matrix formalism,we obtain the general analytical expression of the off-diagonal matrix element responsible for the linear response of probe field.In light of the well-known three-level EIT and ATScriteria,we numerically show an intersection of EIT with ATS.Furthermore,we show that an EIT dip is sandwiched between two ATS dips(i.e.,multi-dip mixture of EIT and ATS)in the absorption line for the five-level system,which can be explained by the dressed-state theory and Fano interference.