The Resonance Fluorescence Of Cascaded Three-level Atoms In A Single-mode Cavity

The interaction between atoms and light fields has always been an important regime in quantum optics.The manipulation of fluorescence radiation has long been an important topic not only in quantum optics,nonlinear optics,but also in laser physics.Sharp spectral line and high intensity are of great significance to enhance the accuracy and efficiency in high-precision measurements,thus it is necessary to explore new methods of narrowing the spectral lines and enhancing the intensity of luorescence spectrum.As we all known,resonance fluorescence spectrum of two-level atoms under the action of a strong driving field presents three-peak structure,while five peaks or even seven peaks would be manifested in the case of three-level atoms.With further exploration by researchers,sharper spectral line and higher intensity of fluorescence spectra have gradually been long-term goals,especially in the system of three-level atoms.In this thesis,we mainly discuss the resonance fluorescence spectrum ofΞ type three-level atoms coupled by a single mode cavity,explore how to narrow the spectral line and enhance intensity of the fluorescence spectrum,the influence of the atomic coherent effect on fluorescence spectra is analyzed in detail.Based on the theory of dressed state,and we choose the appropriate rotating frame,the effect Hamiltonian of the system are acquired.Starting from the Langevin equation,the steady-state solution of operators related to atoms and fields are calculated,then,diffusion coefficient D and the drift coefficient B are given according to the generalized Einstein relation and the linearized Langevin equation respectively,finally,we can get fluorescence spectra of atoms after a series of complicated computational process.The results reveal that,firstly,the cavity field amplification below threshold leads to the spectral narrowing at a pair of inner sidebands while the case of the cavity field amplification above threshold leads to the spectral narrowing at all five spectral peak.Secondly,the case of cavity field coupled transition channel has certain influence on the fluorescence spectrum of no cavity coupled transition,the fluorescence spectrum of both the cavity coupled transition and the no cavity coupled transition show obvious narrowing.Our study offers a deeper understanding of atomic coherent effect in the interaction of atoms with light fields,and may provide a new respective for the experiment relevant to high precision measurement.