Emission of radiation by a system of identical excited three-level emitters

Daniel F. Walls

Qurrat-ul-Ain Gulfam

Fluorescent photon emission probability from a system of three atoms has been studied as a function of detection angles. The system under investigation consists of identical bi-level atoms forming an equilateral triangle. Only a single atom in the triangle is resonantly excited by a weak laser. The interaction mechanism among the atoms is the vacuum-mediated dipole–dipole interaction and the collective decay process. The focus is to analyse the photon pairs simultaneously radiated by the system in the far-field domain. The analysis has been done for various interatomic separations. It is seen that the interference between the photon emitters can lead to strong emission in certain directions. An intuitive understanding of the interesting directions for strong photon bunching is given. It is found that a reduction in the intensity of radiation leads to superradiance along specific directions.

Tracy Tsai

V. E. Lembessis, A. Lyras, Anwar Al Rsheed +2 more

We study the directional properties of a radiation field emitted by a geometrically small system composed of two identical two-level emitters located at short distances and driven by an optical vortex beam, a Laguerre-Gaussian beam which possesses a structured phase and amplitude. We find that the system may operate as a nanoantenna for controlled and tunable directional emission. Polar diagrams of the radiation intensity are presented showing that a constant phase or amplitude difference at the positions of the emitters plays an essential role in the directivity of the emission. We find that the radiation patterns may differ dramatically for different phases and amplitude differences at the positions of the emitters. As a result the system may operate as a two- or one-sided nanoantenna. In particular, a two-sided highly focused directional emission can be achieved when the emitters experience the same amplitude and a constant phase difference of the driving field. We find the general directional property of the emitted field that when the phase differences at the positions of the emitters equal an even multiple of $\ensuremath{\pi}/4$, the system behaves as a two-sided antenna. When the phase difference equals an odd multiple of $\ensuremath{\pi}/4$, the system behaves as a one-sided antenna. The case when the emitters experience the same phase but different amplitudes of the driving field is also considered and it is found that the effect of different amplitudes is to cause the system to behave as a unidirectional antenna radiating along the interatomic axis.

R Palacino, Roberto Passante, L Rizzuto +2 more

Abstract We consider the radiative properties of a system of two identical correlated atoms interacting with the electromagnetic field in its vacuum state in the presence of a generic dielectric environment. We suppose that the two emitters are prepared in a symmetric or antisymmetric superposition of one ground state and one excited state and we evaluate the transition rate to the collective ground state, showing distinctive cooperative radiative features. Using a macroscopic quantum electrodynamics approach to describe the electromagnetic field, we first obtain an analytical expression for the decay rate of the two entangled two-level atoms in terms of the Green’s tensor of the generic external environment. We then investigate the emission process when both atoms are in free space and, subsequently, when a perfectly reflecting mirror is present, showing how the boundary affects the physical features of the superradiant and subradiant emission by the two coupled emitters. The possibility to control and tailor radiative processes is also discussed.