Dynamics of Polariton‐Polariton Interactions in Large‐Area van der Waals Superlattices—Ag Nanohole Arrays Strong Coupling System

The realization of strong and effective optical nonlinear response is a challenging task, which can drive significant breakthroughs in quantum and nonlinear optics. Constructing strongly coupled exciton‐polaritons offers a promising alternative to control nonlinear optical properties. Here we demonstrate strong coupling between Bloch surface plasmon polaritons (Bloch‐SPPs) supported by centimeter‐scale Ag nanoholes (Ag‐NHs) arrays and A excitons in WS 2 ‐based van der Waals superlattices. Angle‐resolved transient absorption (TA) spectroscopy reveals clear anticrossing dispersion with Rabi splitting energies increasing from 61 meV for one monolayer to 120 meV for four monolayer superlattices strong coupling systems. More importantly, pump‐fluence‐dependent TA measurements demonstrate that the observed giant nonlinearity arises predominantly from Coulomb repulsive interactions between polaritons, rather than the phase‐space filling effect. These results highlight a scalable platform for engineering strong polariton‐polariton interactions and pave the way for large‐area, integrable room‐temperature polaritonic nonlinear devices.