Optical response of a binary atomic system with incoherent gain

Abstract

We study the optical response of a binary system of identical atoms in which one of them is excited by an incoherent pump. %We study the properties of photon scattering, absorption and emission, together with the time evolution of the atomic system. %This allows us to characterize and eventually manipulate the state of the system, paving the way for prospective applications in quantum information processing. Applying the diagrammatic formalism developed in Donaire [Phys. Rev. A104, 043704 (2021)], it is shown how scattering, absorption, stimulated emission, spontaneous emission and resonant energy transfer can be tailored by varying i) the interatomic distance, which governs the interference effects of the emitted radiation; and ii) the pump rate, which determines the population of the atomic levels. It is found that, for sufficiently strong pumping, the collective component of the extinction cross-section becomes negligible, regardless of the interatomic distance, as optical gains compensate for losses, and the total extinction cross-section is reduced to less than half of its value in the absence of pumping. In contrast, at weak pumping and short interatomic distances, interference effects lead to a significant suppression of the extinction cross-section relative to that of two noninteracting atoms.