Coherent optical effects in a three-level quantum emitter near a periodic plasmonic nanostructure

Abstract

We investigate optical effects in a three-level $V$-type quantum system involving two closely situated upper levels (a doublet), interacting with a weak probe field while located near a two-dimensional array of metal-coated dielectric nanospheres. We demonstrate that the presence of the plasmonic nanostructure leads to a significant modification of the absorption and dispersion properties of the quantum $V$ system, yielding either very narrow resonances or induced transparency for the weak probe field. Introducing a weak incoherent pumping field can result in gain with and without population inversion in the quantum system, without the need for a strong coherent pump field. Such a gain can be controlled by varying the distance of the quantum system from the plasmonic nanostructure and by adjusting the amount of incoherent pumping, as well as the doublet splitting. The threshold limits are provided both analytically and numerically for achieving gain with and without inversion using the incoherent pumping. Our analysis paves the way toward further theoretical and experimental studies for mitigating dissipative losses in plasmonic modes when the gain is difficult to achieve due to impractical pumping requirements.