Strong coupling of optical nanoantennas and atomic systems

TL;DR

This paper explores the conditions and design principles for achieving strong optical coupling between nanoantennas and atomic systems, demonstrating how this affects observable spectra and potential nanoscale quantum applications.

Contribution

It provides an analytical criterion for quantum description necessity and proposes a nanoantenna design enabling strong coupling with atomic systems.

Findings

Strong coupling leads to significant modifications in extinction spectra.

The spectra are highly sensitive to the number of atomic systems coupled.

A specific nanoantenna design facilitates the strong coupling regime.

Abstract

An optical nanoantenna and adjacent atomic systems are strongly coupled when an excitation is repeatedly exchanged between these subsystems prior to its eventual dissipation into the environment. It remains challenging to reach the strong coupling regime but it is equally rewarding. Once being achieved, promising applications as signal processing at the nanoscale and at the single photon level would immediately come into reach. Here, we study such hybrid configuration from different perspectives. The configuration we consider consists of two identical atomic systems, described in a two-level approximation, which are strongly coupled to an optical nanoantenna. First, we investigate when this hybrid system requires a fully quantum description and provide a simple analytical criterion. Second, a design for a nanoantenna is presented that enables the strong coupling regime. Besides a vivid time evolution, the strong coupling is documented in experimentally accessible quantities, such as the extinction spectra. The latter are shown to be strongly modified if the hybrid system is weakly driven and operates in the quantum regime. We find that the extinction spectra depend sensitively on the number of atomic systems coupled to the nanoantenna.