Expanding the hot-spot distribution in hybrid Nanohole Arrays toward high-performance light trapping

Trapping light and enhancing electromagnetic fields in plasmonic nanostructures are crucial for advanced applications, such as for surface-enhanced Raman scattering, surface-enhanced fluorescence and plasmon-enhanced second-harmonic generation (PESHG) at subwavelength scales. Expanding the spatial distribution of enhanced electromagnetic fields, i.e., hot spots, has become a vital strategy to significantly enhance the performance of advanced nanophotonic applications. In this work, we propose a strategy of hybrid metal-dielectric (MD) nanohole arrays by introducing low-loss silicon nitride (Si ₃ N ₄ ) dielectric layers into aluminum (Al) nanohole arrays to realize the strong light-trapping and expand the spatial distribution of hot spots at MD interfaces by changing the diameter of nanohole. The mechanism governing these phenomena is deriving from the occurrence of dielectric-mediated plasmonic coupling, facilitating the translation of local light confinements governed by plasmon-driven resonances to dielectric components and LSPR-excited hot-spots redistribution in plane. Moreover, we introduce both label and label-free optical probes regarding the photoluminescence enhancement of MoS ₂ and PESHG to verify and quantify the effect of expanded hot-spot distribution in hybrid Al-Si ₃ N ₄ nanohole arrays on the enhancement of light-matter interaction. This work may provide a theoretical and experimental mechanism for expanding the potential in characterizing and quantifying hot-spot distribution in advanced optical nanodevices.