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The valley degree of freedom that results from broken inversion symmetry in two-dimensional (2D) transition-metal dichalcogenides (TMDCs) has sparked a lot of interest due to its huge potential in information processing. In this experimental work, to optically address the valley-polarized emission from three-layer (3 L) thick WS₂at room temperature, we employ a SiN photonic crystal slab that has two sets of holes in a square lattice that supports directional circular dichroism engendered by delocalized guided mode resonances. By perturbatively breaking the inversion symmetry of the photonic crystal slab, we can simultaneously manipulate s and p components of the radiating field so that these resonances correspond to circularly polarized emission. The emission of excitons from distinct valleys is coupled into different radiative channels and hence separated in the farfield. This directional exciton emission from selective valleys provides a potential route for valley-polarized light emitters, which lays the groundwork for future valleytronic devices.

Room temperature stable excitons in layered two‐dimensional (2D) transition metal dichalcogenides (TMDs) offer a unique route for engineering light and matter interactions. Due to the strong optical dispersion near the excitonic transitions, a high refractive index arises in these ultrathin semiconductors.^[1,2]Utilizing this behavior, strongly confined Fano type optical resonances in an ultrathin (i.e., ≈12 nm) tungsten disulfide (WS₂) photonic crystal (PhC) directly fabricated on a TMD‐on‐glass platform are reported. In this approach, Fano‐type WS₂photonic resonances strongly couple to the WS₂excitonic dispersion engender self‐resonant exciton‐polaritons with an out‐of‐plane optical confinement exceeding that provided by surface plasmon polaritons in the visible. The large spatial light‐matter overlap endowed by this unique monolithic self‐coupling scheme is utilized for steering of enhanced 2D WSe₂excitonic photoluminescence in a truly TMD integrated system. It is envisioned that the strong light matter interaction on the TMD‐on‐glass platform will unfold the prospects of ultrathin exciton‐polaritonic resonators.