Polariton-Mediated Ultrafast Nonlinear Energy Transfer in a van der Waals Superlattice

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Exciton-polariton dynamics in 2D materials have garnered substantial attention across diverse scientific domains for fundamental research with potential applications in optoelectronics. However, practical implementation has been hindered by the challenge of maintaining stable and long-range polariton propagation. Here, we present an innovative material platform featuring extensive monolayer WS₂/Al₂O₃ superlattices (a square with a length of >0.5 cm) coupled to a waveguide mode designed to host exciton-polaritons with operation at room temperature. Time-resolved transient absorption spectra show picosecond nonlinear energy transfer phenomena between upper and lower polariton states, clarifying the dynamic behavior within this quantum realm. In addition, we observed population inversion behavior between the two polariton states that facilitate potential avenues for creating polariton-based ultrafast modulators and switches. This research not only advances our fundamental understanding of polariton dynamics but also promotes the development of innovative technologies that harness these fascinating quantum phenomena.