Spontaneous emission and absorption properties of a driven three-level system

Abstract

We investigate the steady-state spontaneous emission spectrum of a three-level atom driven by two coherent fields and the absorption spectrum of a weak probe passing through a collection of such driven atoms. We find that the fluorescence spectrum is strongly affected by the decay rates of all the levels involved in the atomic evolution and not just by the decay parameters of the specific transition whose emission spectrum is being monitored. In particular, the spectral components can acquire very different widths and peak heights relative to the case of the standard resonance fluorescence in which a two-level system is driven by a single near-resonant field. An external probe signal passing through the gas of three-level atoms may be absorbed or amplified, as in the standard twolevel case, but under specific operating conditions, amplification (or absorption} occurs over the entire range where the atomic response is appreciable. In this case the existence of amplification or absorption is controlled solely by the population difference between two dressed states of the system. We provide numerical results in support of our arguments for arbitrary values of the atomic and field parameters and also develop an analytic description in the limit of strong driving fields that leads to explicit line-shape and linewidth formulas.

Cavity implementation of quantum interference in aΛ-type atom

“…For example, for three-level atomic systems (in V , Λ and Ξ configurations) excited by two laser fields: one being a strong pump field to drive two levels (say |1 and |2 ) and the other being a weak probe field at different frequency to probe the levels |0 and |1 or |2 , the strong coherent field can drive the levels |1 and |2 into superpositions of these states, so that different atomic transitions are correlated. For such systems, the cross-transition terms are evident in the atomic dressed picture [3,8,12]. A four-level atom with two closely-spaced intermediate states coupled to a two-mode cavity can also show the effect of quantum interference [10].…”

“…It is important for these effects that the dipole moments of the transitions involved are parallel, so that the cross-transition terms are maximal. From the experimental point view, however, it is difficult to find isolated atomic systems which have parallel moments [2,6,[9][10][11].Various alternative proposals [3,8,10,12] have been made for generating quantum interference effects. For example, for three-level atomic systems (in V , Λ and Ξ configurations) excited by two laser fields: one being a strong pump field to drive two levels (say |1 and |2 ) and the other being a weak probe field at different frequency to probe the levels |0 and |1 or |2 , the strong coherent field can drive the levels |1 and |2 into superpositions of these states, so that different atomic transitions are correlated.…”

“…The gain occurring at different sidebands has the various origin: in the case of δ > 0, the higher-frequency gain is due to the nonzero coherence, while the lower-frequency one is attributed to the population inversion. As shown in Refs: [3,8,12] that an apply laser coupling to multilevel atoms may result in the steady-state coherence and population inversions. We here present an another scheme whereby they can be generated by the cavity-induced interference.…”

“…Gy, 42.50.Ct, Within recent years, there has been a resurgence of interest in the phenomenon of quantum interference between different transition paths of atoms [1]. The principal reason is that it lies at the heart of many new effects and applications of quantum optics, such as lasing without population inversion [2], electromagnetically-induced transparency [3], enhancement of the index of refraction without absorption [4], fluorescence quenching [5][6][7], spectral line narrowing [7,8].The basic system consists of a singlet state connected to a closely-spaced doublet by a single electromagnetic vacuum interaction [6,7,9], so that the two transition pathways from the doublet states to the singlet are not independent and may interfere. It is important for these effects that the dipole moments of the transitions involved are parallel, so that the cross-transition terms are maximal.…”

“…Various alternative proposals [3,8,10,12] have been made for generating quantum interference effects. For example, for three-level atomic systems (in V , Λ and Ξ configurations) excited by two laser fields: one being a strong pump field to drive two levels (say |1 and |2 ) and the other being a weak probe field at different frequency to probe the levels |0 and |1 or |2 , the strong coherent field can drive the levels |1 and |2 into superpositions of these states, so that different atomic transitions are correlated.…”