Steady-state quantum interference in resonance fluorescence

Abstract

Abstract. It is shown that when a monochromatic laser couples a single atomic ground level to two closely spaced excited levels the system can be driven into a state in which quantum interference prevents any fluorescence from the excited levels, regardless of the intensity of the exciting field. This steady-state interference occurs only at a particular excitation frequency which depends on the separation of the excited states and the relative size of the two transition dipole matrix elements. The results are derived from the density matrix equations of motion. It is shown that a correct description of the effect requires the inclusion of generalised Einstein A coefficients which are usually neglected in phenomenological damping theories. A dressed-state analysis is introduced to simplify the generalisation to atoms having more complex manifolds of excited states. Analogous interferences in multiphoton absorption and ionisation are also discussed briefly.

Cavity implementation of quantum interference in aΛ-type atom

“…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.…”

“…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.…”

“…As pointed out in Refs. [2,6,10,11] however, it is questionable whether there is a isolated atomic system with parallel dipoles. Otherwise, if the polarization of the cavity mode is fixed, say e λ = e x , the polarization direction along the x-quantization axis, then…”

“…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.…”

“…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].…”