Interference Phenomena in Spontaneous Emission from Driven Multilevel Atoms

We study spontaneous emission from an atom under the action of laser fields. We consider two different energy level diagrams. The first one consists of two levels resonantly driven by laser radiation where either of levels may decay to a separate level. For such a system we show that the presence of the second decay channel may deteriorate the destructive interference occurring in case of one decay channel because of Autler-Townes effect. The second diagram represents two two-level resonantly driven systems with the upper levels decaying to a common level. For this diagram we show that there is no interference between the two decay channels when the laser fields are described in the Fock representation, while in case of definite-phase classical fields such interference takes place and is partially or completely destructive or constructive depending on the initial conditions and on the mutual orientation of the spontaneous emission dipole moments.