Strong Plasmon–Exciton Coupling in Ag Nanoparticle—Conjugated Polymer Core-Shell Hybrid Nanostructures

Abstract

Strong plasmon–exciton coupling between tightly-bound excitons in organic molecular semiconductors and surface plasmons in metal nanostructures has been studied extensively for a number of technical applications, including low-threshold lasing and room-temperature Bose-Einstein condensates. Typically, excitons with narrow resonances, such as J-aggregates, are employed to achieve strong plasmon–exciton coupling. However, J-aggregates have limited applications for optoelectronic devices compared with organic conjugated polymers. Here, using numerical and analytical calculations, we demonstrate that strong plasmon–exciton coupling can be achieved for Ag-conjugated polymer core-shell nanostructures, despite the broad spectral linewidth of conjugated polymers. We show that strong plasmon–exciton coupling can be achieved through the use of thick shells, large oscillator strengths, and multiple vibronic resonances characteristic of typical conjugated polymers, and that Rabi splitting energies of over 1000 meV can be obtained using realistic material dispersive relative permittivity parameters. The results presented herein give insight into the mechanisms of plasmon–exciton coupling when broadband excitonic materials featuring strong vibrational–electronic coupling are employed and are relevant to organic optoelectronic devices and hybrid metal–organic photonic nanostructures.

Optical Spectra of Plasmon--Exciton Core--Shell Nanoparticles: A Heuristic Quantum Approach

“…It was attributed to a so-called shell mode where the Lorentzian coating attains metallic character (a negative real part of the Lorentzian permittivity). 15 This spurious third peak, which also appeared in other published simulations, [16][17][18] marks a clear contradiction to the usual models, as the masses-andsprings model or a simple quantum mechanical model for strong coupling predict only two polariton peaks. 19 And experimentally, such a third peak has never been observed.…”

Optical Spectra of Plasmon–Exciton Core–Shell Nanoparticles: A Heuristic Quantum Approach

“…It was attributed to a so-called shell mode or surface exciton polariton mode, , where the Lorentzian coating attains a metallic character (a negative real part of the Lorentzian permittivity). This spurious third peak, which also appeared in other published simulations, − marks a clear contradiction to the usual models, as the masses-and-springs model or a simple quantum mechanical model for strong coupling predict only two polariton peaks . And experimentally, such a third peak has never been observed in spectra of pure core–shell particles (only in samples with residual, uncoupled emitters − ).…”

Quantum nanophotonic and nanoplasmonic sensing: towards quantum optical bioscience laboratories on chip

“…Computational methods are very useful for studying strong coupling in plasmon-emitter systems and can be used to accelerate research in this field. Classical electromagnetism simulations, using finite-difference time-domain methods or finite element methods, have been used to predict and optimize plasmonic-emitter configurations that would lead to strong coupling before doing experiments [313][314][315]. The strong coupling regime has also been explored with ab initio computational methods, which model the many-electron interactions of the system.…”