Transferable Plasmonic Arrays Enabling Strong Coupling with Layered Perovskites in an Active Diode Architecture

Plasmonic cavities provide a powerful platform for nanoscale light confinement far beyond the diffraction limit, enabling exceptionally strong light-matter interactions. Recent advances in plasmonic architectures and active materials enable stable, scalable routes toward fully integrated on-chip photonics. In this work, we demonstrate the strong coupling of 2D layered perovskites with a transferable plasmonic cavity directly fabricated on top of hexagonal boron nitride (hBN). Under optical excitation, we observe clear interaction between the exciton and cavity modes leading to strong and even ultrastrong coupling, with coupling factors g up to 10% of the resonance energy. Combined with the polariton mode hybridization and a waveguiding effect, this results in pronounced line width narrowing of the polariton modes well below both the bare cavity and exciton line widths. Electrical excitation of the hybrid modes is achieved via electron tunneling and simultaneous energy transfer, making this design an attractive configuration for on-chip integration.