Modification of the resonance fluorescence spectrum of a two-level atom in the near field of a plasmonic nanoparticle

The resonance fluorescence spectrum of an atom located in the near field of a plasmonic nanoparticle is considered. It is shown that, as the atom gets close to the nanoparticle, the high-frequency peak of the Mollow triplet disappears and the spectrum has a Fano resonance shape. The low-frequency peak also disappears as the distance between the atom and the nanoparticle decreases further. For small distances, when the atom interacts with the nanoparticle much more strongly than with the external field, the spectrum represents a Lorentzian line whose width is proportional to the square of the atom-nanoparticle coupling constant.