Absorption and photoluminescence properties of coupled plasmon-exciton (plexciton) systems

TL;DR

This paper develops a classical oscillator model to analyze the optical properties of plexciton systems, revealing strong coupling effects like electromagnetically induced transparency, mode splitting, and enhanced photoluminescence, validated by experimental comparisons.

Contribution

The study introduces a detailed theoretical model for plexciton behavior, elucidating strong coupling phenomena and photoluminescence enhancement in hybrid plasmon-exciton systems.

Findings

Electromagnetically induced transparency observed in absorption spectra.

Mode splitting depends on electron number and resonance coupling.

Photoluminescence intensity can be significantly enhanced.

Abstract

Plexciton is the formation of new hybridized energy states originated from the coupling between plasmon and exciton. To reveal the optical properties of both exciton and plexciton, we develop a classic oscillator model to describe the behavior of them. Particularly, the coupling case, i.e., plexciton, is investigated theoretically in detail. In strong coupling, the electromagnetically induced transparency is achieved for the absorption spectra; the splitting behaviors of the modes are carefully analyzed, and the splitting largely depends on the effective number of the electrons and the resonance coupling; the photoluminescence spectra show that the spectral shapes remain almost unchanged for weak coupling and change a lot for strong coupling; the emission intensity of the exciton is strongly enhanced by the plasmon and can reach to the order of $10^{10}$ for a general case. We also show the comparisons between our model and the published experiments to validate its validity. This work may be useful for understanding the mechanism of the plexciton and for the development of new applications.