OGRES

The nanoparticle-on-mirror (NPoM) configuration is a plasmonic system where a metallic nanoparticle, often a nanocube, is placed above a flat metallic surface, separated by a nanometer-thin dielectric gap. This structure supports a gap-plasmon (GP) mode, which is highly confined and enhances the electromagnetic field more efficiently than traditional surface plasmon resonance (SPR) systems. The reflection of plasmonic modes beneath the nanoparticle leads to a resonance similar to a laser cavity, further strengthening field enhancement. These properties make NPoM a promising platform for sensing applications, as the system is highly responsive to changes in refractive index, spacer thickness and composition, and nanoparticle size and shape.

While tuning individual nanoparticle properties has shown to optimize resonance, coupled NPoM architectures, involving interactions between multiple nanoparticles, could lead to even greater field enhancements. However, optimizing, fabricating and characterizing these complex plasmonic architectures is challenging.

This project aims to gain a deeper understanding of coupling mechanisms in single and multi-nanoparticle NPoM structures, particularly interactions between the nanocube and the metallic substrate, as well as between neighboring nanocubes. Artificial intelligence-based optimization and inverse design will focus on enhancing field confinement, sensitivity, and selectivity for improved sensing performance. The research combines:

• Nanocube-based NPoM synthesis (CINaM expertise),
• AI-based optimization and inverse design (IM2NP expertise),
• Advanced nanometrology techniques, including scattering-Scanning Nearfield Optical Microscopy (s-SNOM) (Fresnel expertise) and cathodoluminescence (CL) (HZDR expertise).

By mapping the electromagnetic field around and beneath nanocubes, this study will investigate plasmonic mode coupling, decoupling, and radiation leakage into the surrounding environment. These insights will facilitate the design of AI-optimized NPoM architectures for enhanced sensing applications.

The ultimate goal is to develop and test an optimized NPoM-based optical sensor for environmental monitoring, particularly in detecting volatile organic compounds (VOCs). The project aims to position this technology at a competitive level in the field of optical sensing, contributing to advanced real-world detection solutions.