Two-dimensional exciton–polariton—light guiding by transition metal dichalcogenide monolayers

Two-dimensional (2D) monolayer-thick materials with a direct bandgap, such as MoS, WSe, and other transition metal dichalcogenides (TMDCs), are being actively explored for future nanophotonic applications in the visible and UV ranges. Here I show that a monolayer of TMDCs is capable of supporting a guided optical mode below the exciton resonance—a 2D exciton–polariton. I evaluate the characteristics of these guided modes and conditions required for their existence, including derivations of mode dispersion relations, mode confinements, and propagation lengths. The visible or near-IR mode is confined to within roughly a micrometer of the monolayer and has a propagation length exceeding 100 μm. This light guiding ability in the visible and IR ranges makes TMDC monolayers a versatile and potentially attractive platform for future optoelectronic devices.