Plexcitonic Quantum Light Emission from Nanoparticle-on-Mirror Cavities

Abstract

We investigate the quantum-optical properties of the light emitted by a nanoparticle-on-mirror cavity filled with a single quantum emitter. Inspired by recent experiments, we model a dark-field setup and explore the photon statistics of the scattered light under grazing laser illumination. Exploiting analytical solutions to Maxwell’s equations, we quantize the nanophotonic cavity fields and describe the formation of plasmon–exciton polaritons (or plexcitons) in the system. This way, we reveal that the rich plasmonic spectrum of the nanocavity offers unexplored mechanisms for nonclassical light generation that are more efficient than the resonant interaction between the emitter natural transition and the brightest optical mode. Specifically, we find three different sample configurations in which strongly antibunched light is produced. Finally, we illustrate the power of our approach by showing that the introduction of a second emitter in the platform can enhance photon correlations further.

A Theoretical Perspective on Molecular Polaritonics

“…Since subwavelength confinement is a prerequisite for the quasistatic approximation, these material losses will always be significant . One advantage of the quasistatic approximation is that the EM modes can be described by a scalar potential, which simplifies the treatment of beyond-dipole interactions. − Another advantage of the quasistatic approximation is that for metals described by a dielectric function of Drude form the resulting eigenmodes will always correspond to uncoupled Lorentzians in the spectral density (discussed in more detail below), which allows for a straightforward quantization procedure of the resulting modes. ,, Radiative losses can also be included a posteriori, e.g., by calculating the effective dipole moment of the localized resonances. ,, These quasistatic treatments of plasmonic modes have led to analytical insights into different aspects of strong light–matter coupling in metal nanostructures. On one hand, they have shown that molecular degrees of freedom such as the presence of light-forbidden transitions can be harnessed to tailor polaritonic properties. , On the other hand, they have also revealed different strategies to exploit the polaritonic (originally excitonic) quantum nonlinearities for nonclassical light generation in these deeply subwavelength systems …”

“…88,90,91 Radiative losses can also be included a posteriori, e.g., by calculating the effective dipole moment of the localized resonances. 88,92,93 These quasistatic treatments of plasmonic modes have led to analytical insights into different aspects of strong light−matter coupling in metal nanostructures. On one hand, they have shown that molecular degrees of freedom such as the presence of light-forbidden transitions can be harnessed to tailor polaritonic properties.…”

“…88,92 On the other hand, they have also revealed different strategies to exploit the polaritonic (originally excitonic) quantum nonlinearities for nonclassical light generation in these deeply subwavelength systems. 93 When the quasistatic approximation is not appropriate and retardation effects have to be taken into account, the most general and powerful approach to nonetheless obtain a quantized description of the EM field is macroscopic QED. This is a formalism that quantizes the EM field in arbitrary structures, including dispersive and absorbing materials.…”

Effective Single-Mode Methodology for Strongly Coupled Multimode Molecular-Plasmon Nanosystems

“…Strong light–matter coupling between molecules and electromagnetic fields leads to the formation of new hybrid states, known as polaritons, where the quantum nature of the electromagnetic field entangles with purely molecular states. − The resulting polaritons can display different key features compared to the original states, potentially leading to new chemical/photochemical reactivity, ,− energy transfer processes, − or relaxation channels, ,− among others. While photonic cavities are an obvious choice, other fields, like the ones produced by electronic excitations in plasmonic nanostructure, can also be used to achieve the strong coupling regime.…”

Electroluminescence as a Probe of Strong Exciton–Plasmon Coupling in Few-Layer WSe2

“…The optical response of the strongly coupled system is highly sensitive to the state of the photon emitter(s), 7 which provides a means of manipulating quantum states of light and can enable high-fidelity quantum operations 9−11 and nonclassical photon generation. 12,13 Transition-metal dichalcogenides (TMDs) are ideal materials for coupling to optical resonators, as TMDs interact strongly with light through sharp excitonic modes with high binding energies of a few hundred meV even at room temperature, 14 particularly in the monolayer limit. 15−18 Embedding the strong dipole moment of these optical transitions in EM resonators has enabled the formation of hybrid, polariton states whose matter components are TMD excitons.…”