Optimizing Plasmonic Couplingin Gold Nanoparticle Metasurfaces: A Theoretical Investigation

Abstract

This study investigates the plasmonic response of gold nanoparticle metasurfaces using the theory of thin island films. It explores how factors such as nanoparticle shape, size, surface coverage, and anisotropy influence localized surface plasmon resonances(LSPRs). Spherical nanoparticles exhibit a single LSPR dip, with an increase in size leading to a red shift and enhanced resonance strength. Surface coverage modulates plasmonic coupling, with moderate values that enhance interactions, while excessive coverage leads to plasmon hybridisation and resonance broadening. Oblate spheroidal nanoparticles exhibit anisotropy-induced mode splitting in p-polarization and a redshiftin s-polarization, with higher anisotropy enhancing the plasmonic response. The conditions for critical coupling, where reflectance approaches zero, are identified as functions of particle size, coverage, and anisotropy. These findings provide insights into tuning the properties of LSPRs in thin island films for applications in plasmonic sensing and photonics.