Enhanced Exciton–Plasmon Interaction Enabling Observation of Near-Field Photoluminescence in a WSe2–Gold Nanoparticle Hybrid System

Monolayer transition metal dichalcogenides, such as tungsten diselenide, have recently attracted considerable attention due to their reduced dielectric screening and direct bandgap, which result in high exciton binding energy and strong photoluminescence. The integration of monolayer transition metal dichalcogenides with plasmonic nanoparticles enhances their optoelectronic properties through localized surface plasmons and strong electromagnetic confinement. We investigated the photoluminescence response of the hybrid system of monolayer tungsten diselenide and gold nanoparticle arrays through near-field mapping. Our study demonstrated a significant enhancement of the excitonic emission by the excited gold nanoparticles via near-field interaction. We examined the impact of exciton–plasmon-polariton coupling on the far-field response of the hybrid system. There, we observed the phenomenon of exciton-induced transparency, which indicates the intermediate coupling regime and helps resonantly enhance the light-matter interaction in monolayer tungsten diselenide. The second harmonic generation intensity from the hybrid system was shown to follow the linear spectral response of the hybrid system, thereby demonstrating the enhanced coupling between surface plasmons and excitons. Our research offers insights into the impact of intermediate coupling on the optical properties of hybrid exciton–plasmon systems, which is crucial for the development of advanced nanophotonic devices.