Radiation pattern of two identical emitters driven by a Laguerre-Gaussian beam: An atom nanoantenna

TL;DR

This paper investigates how two identical quantum emitters driven by a Laguerre-Gaussian beam can function as a tunable nanoantenna with controllable directional radiation patterns, depending on phase and amplitude differences.

Contribution

It introduces a novel approach to control nanoantenna directivity using structured optical vortex beams and phase/amplitude tuning of emitters.

Findings

Achieves highly focused two-sided directional emission with same amplitude and phase difference.

Identifies phase difference conditions for one-sided and two-sided antenna behavior.

Demonstrates control of emission directionality via phase and amplitude adjustments.

Abstract

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 phase 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 a general directional property of the emitted field that when the phase differences at the positions of the emitters equal an even multiple of \pi/4, the system behaves as a two-sided antenna. When the phase difference equals an odd multiple of \pi/4, the system behaves as an 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 uni-directional antenna radiating along the interatomic axis.