Strong coupling out of the blue: an interplay of quantum emitter hybridization with plasmonic dark and bright modes

TL;DR

This paper demonstrates that a single quantum emitter can achieve strong coupling with plasmonic dark modes, leading to vacuum Rabi splitting and single-photon non-linearity, which advances room temperature quantum plasmonics.

Contribution

It reveals that dark plasmonic modes can be hybridized with detuned electronic transitions of quantum emitters to achieve strong coupling, expanding the understanding of plasmon-emitter interactions.

Findings

Vacuum Rabi splitting achieved via dark mode hybridization.

Detuned electronic transitions can couple with dark plasmon pseudomodes.

Single photon non-linearity demonstrated in the dark strong coupling regime.

Abstract

Strong coupling between a single quantum emitter and an electromagnetic mode is one of the key effects in quantum optics. In the cavity QED approach to plasmonics, strongly coupled systems are usually understood as single-transition emitters resonantly coupled to a single radiative plasmonic mode. However, plasmonic cavities also support non-radiative (or "dark") modes, which offer much higher coupling strengths. On the other hand, realistic quantum emitters often support multiple electronic transitions of various symmetry, which could overlap with higher order plasmonic transitions -- in the blue or ultraviolet part of the spectrum. Here, we show that vacuum Rabi splitting with a single emitter can be achieved by leveraging dark modes of a plasmonic nanocavity. Specifically, we show that a significantly detuned electronic transition can be hybridized with a dark plasmon pseudomode, resulting in the vacuum Rabi splitting of the bright dipolar plasmon mode. We develop a simple model illustrating the modification of the system response in the "dark" strong coupling regime and demonstrate single photon non-linearity. These results may find important implications in the emerging field of room temperature quantum plasmonics.