We give an analytical expression of emission spectrum for two different two-level atoms interacted with one-mode field. The effect of initial state of system on the emission spectrum for two-level atoms is explored, and the conditions leading to atom coherent population trapping are investigated.
The emission spectrum of a pair of two-level atoms interacting with a single mode of radiation field in an ideal cavity is investigated, where the interaction of each atom with the field may be different. A general expression for the emission spectrum is presented and the spectrum is studied numerically when the radiation field is initially in the vacuum state, pure number state and squeezed-vacuum state, respectively. The effects of the ratio of two coupling constants (R=g 2 /g 1 ) on the emission spectrum are discussed. In contrast with the spectrum of a one-atom system, the spectrum of a two-atom system is much more complicated. Generally, the emission spectrum shows a 12-peak structure for the vacuum state and 16-peak structure for the pure number state. For the squeezed-vacuum state, it is found that the Rabi splitting is most apparent when R=1.
We have studied the atomic coherent population trapping in the system of a two-mode quantized field interacting with a Λ-configuration multilevel atom with one lower discrete state and two sets of quasicontinuum states, or a set of quasicontinuum states and a set of true continuum states. The influence of the atom's initial preparation and the properties of the atomic upper levels on whether or not atomic coherent population trapping occurs, and the states of the field which trap the atom are analyzed.
We study the influence of quantum interference on the spontaneous emission from an excited two-level atom when either the atomic upper or lower level is coupled by a coherent field to a third, usually higher-lying, state. In the case of the upper level coupling, destructive quantum interference between two competing decay amplitudes produces a dark line in the emission spectrum, a phenomenon that should not be confused with the well known population trapping, and a narrowing of one of the two side lobes that make up the spectral profile. Quantum interference is absent, instead, in the case of the lower level coupling, and the spectrum modified by the external driving field is just the incoherent superposition of two Lorentzian lines. We suggest a physical interpretation of these results. In addition, we compare the analytic predictions of the simplest nontrivial versions of these models with more realistic but nonanalytic descriptions and show, numerically, that the interference effects persist in the upper level case even when additional complications are taken into account.
The emission spectrum of a two-level atom interacting with a single mode radiation field in the case of periodic oscillation coupling coefficient is investigated. A general expression for the emission spectrum is derived. The numerical results for the initial field in pure number stare are calculated. It is found that the effect of the coupling coefficient modulation on the spectral structure is very obvious in the case of a low modulation frequency and larger amplitude when the initial field is vacuum, which is potentially useful for exploring a modulated light source.
The emission spectrum of a two-level atom interacting dispersively with a single mode radiation field in the dissipative cavity is investigated. A general expression for the emission spectrum is derived. The numerical results for the initial field in coherent state are calculated. It is found that the spectrum structure is influenced significantly by the cavity damping constant κ, and the spectrum structure is dependent on the interaction time T when the cavity dissipation is present. Only one peak located at ω a appears in the atomic spectra for larger T.