  Two-dimensional transition metal dichalcogenides (TMDCs) have recently become
attractive semiconductor materials for several optoelectronic applications,
such as photodetection, light harvesting, phototransistors, light-emitting
diodes, and lasers. They are particularly appealing because their bandgap lies
in the visible and near-IR range, and they possess strong excitonic resonances,
high oscillator strengths, and valley-selective response. Coupling these
materials to optical nanocavities enhances the quantum yield of exciton
emission, enabling advanced quantum optics and nanophotonic devices. Here, we
review state-of-the-art advances on hybrid exciton-polariton structures based
on monolayer TMDCs coupled to plasmonic and dielectric nanocavities. We first
generally discuss the optical properties of 2D WS2, WSe2, MoS2 and MoSe2
materials, paying special attention to their energy and
photoluminescence/absorption spectra, excitonic fine structure, and to the
dynamics of exciton formation and valley depolarization. We then discuss
light-matter interactions in hybrid exciton-polariton structures. Finally, we
focus on weak and strong coupling regimes in monolayer TMDCs-based
exciton-polariton systems, envisioning research directions and future
opportunities based on this novel material platform.
