Quasi ¡Ä Type Four Level System Spontaneous Radiation And Absorption Characteristics Of The Study

Spontaneous emission is one of the best known fimdamenta processes resultingfrom the inieraction between radiation and matter. In recent years, qurtum trapping,altering of spontaneous emission and absorption and quantum interference viadifferent transition pathways are hot subjects in the field of quantum optics. Thespontaneous depressed, the spectral profile of spontaneous emission narrowed andcancellation of sponianous emission are put forth, and are verified in the experiments.Spontaneous emission interference conditions and dressed-state representation, whichare gained in the theory, promoted the investigation of spontaneous emission.We investigate quantum-trapping state, the steady-state spontaneous emissionproperty and absorption property of an extemal probe signal passing through the fourlevel system carefully in this paper, and show some numerical results of the theoryWe investigate effects on spectra of various incoherent transition and quantuminterference between different transition pathways. Meanwhile, we look into themechanism in the dressed-state representation. Finally, we verify our theory in asimply three-level system.Through investigation, we conclude that there are great effects on the spectralprofile of the incoherent transitions between the levels. When the rate of theincoherent transition is very small, the spontaneous emission spectrum is very narrow;The faster of the rate of the incoherent transition, the wider of the spontaneousemission spectrum; An extemal probe signal passing through the gas of the four-levelatoms may be absorbed or amplified. But under specific operating condition,amplification(or absorpion ) occurs over the wide spectral range; Quantumintefference via different pathways exists, in another word, there are interferencecancellation or enhancement of spontaneous emission via different pathway; Unlikethe Λ-model-three-level system, there are two coherent trapping state in the quasi-A-model-four-level system; Finally, experiment testify that effects of the incoherenttransitions on the spectra and the quantum interference are exiSt in the simple three-level system.