Effects of exciton-plasmon strong coupling on third harmonic generation of WS2 monolayer at periodic plasmonic interfaces

TL;DR

This paper theoretically investigates how strong exciton-plasmon coupling at periodic plasmonic interfaces enhances third harmonic generation in WS2 monolayers, revealing significant spectral and nonlinear effects useful for nano-probing.

Contribution

It demonstrates the impact of strong exciton-plasmon coupling on third harmonic generation in WS2 monolayers near periodic plasmonic structures, highlighting the role of hybrid modes and local fields.

Findings

Rabi splitting observed in transmission and reflection spectra.

Third harmonic signal is significantly enhanced under strong coupling.

Localized electromagnetic fields are highly sensitive to environmental changes.

Abstract

We study theoretically optical response of WS2 monolayer located near periodic metal nanostructured arrays in two and three dimensions. The emphasis of simulations is on the strong coupling regime of excitons supported by WS2 and surface plasmon-polaritons supported by various periodic plasmonic interfaces. It is demonstrated that a monolayer of WS2 placed in a close proximity of periodic arrays of either slits or holes results in a Rabi splitting of the corresponding surface plasmon-polariton resonance as revealed in calculated transmission and reflection spectra. The nonlinear regime, at which the monolayer of WS2 exhibits the third harmonic generation is studied in details. It is shown that at the strong coupling regime the third harmonic signal is significantly affected by plasmon-polaritons and the symmetry of hybrid exciton-plasmon modes. It is also shown that the local electromagnetic field induced by plasmons is the major contributor to the enhancement of the third harmonic signal in three dimensions. The local electromagnetic fields resulted from the third harmonic generation are greatly localized and highly sensitive to the environment making it a great tool for nano-probes.