Selective Growth of Bulk-Like Perovskite in Plasmonic Nanoholes for Enhanced Two-Photon-Excited Emission.

Plasmon-enhanced nonlinear optical phenomena in hybrid perovskite-plasmonic systems present significant opportunities for photodetection, bioimaging, and quantum light sources. However, achieving uniform growth of luminescent materials within confined plasmonic hotspots remains challenging, as conventional surface deposition or infiltration approaches cannot fill nanocavities effectively. To resolve this, we present a vacuum-assisted capillary infiltration (VACI) strategy for delivering precursor solutions into gold (Au) nanohole (NH) arrays, enabling in situ crystallization within plasmonic cavities. This work demonstrates selective bulk-like cesium lead bromide (CsPbBr3) growth inside NHs through precise infiltration and controlled crystallization. By integrating the capillary effect with vacuum pressure, this approach ensures uniform filling beyond conventional methods. The successful integration of CsPbBr3 was confirmed through peel-off techniques and structural/chemical analyses. Electromagnetic simulations predict an average field enhancement of |E/E0| ≈2.80 at 800 nm, consistent with an experimentally observed ∼40-fold increase in two-photon absorption (TPA)-induced green emission (λ ≈526 nm). Unlike prior TPA systems employing quantum dots, rare-earth doped crystals, or organic chromophores, this approach integrates bulk-like perovskite directly into plasmonic NH cavities. This establishes a general framework for material-structure integration in plasmonics and nanophotonics, and a foundation for infrared photodetection, high-resolution nonlinear imaging, and quantum light sources.