Photoemission electron microscopy of exciton-polaritons in thin WSe$_2$ waveguides

TL;DR

This study uses photoemission electron microscopy to analyze exciton-polaritons in thin WSe$_2$ waveguides, revealing their dispersion and energy splitting, which advances understanding of light-matter interactions in 2D materials.

Contribution

It introduces a novel application of photoemission electron microscopy to directly observe exciton-polariton dispersion and coupling in WSe$_2$ waveguides, providing new insights into their properties.

Findings

Measured dispersion of photonic modes in WSe$_2$ flakes.

Observed Rabi splitting indicating strong exciton-photon coupling.

Established a foundation for time-resolved studies of exciton-polaritons.

Abstract

Exciton-polaritons emerging from the interaction of photons and excitons in the strong coupling regime are intriguing quasiparticles for the potential exchange of energy during light-matter interaction processes such as light harvesting. The coupling causes an energy anti-crossing in the photon dispersion centered around the exciton resonance, i.e., a Rabi splitting between a lower and upper energetic branch. The size of this splitting correlates with the coupling strength between the exciton and the photonic modes. In this work, we investigate this coupling between excitons and photonic waveguide modes excited simultaneously in thin-film flakes of the transition-metal dichalcogenide WSe$_2$. Using a Photoemission electron microscope, we are able to extract the dispersion of the transversal electric and magnetic modes propagating through these flakes as well as extract the energy splitting. Ultimately, our findings provide a basis for the investigation of the propagation of exciton-polaritons in the time-domain via time-resolved photoemission.