Plasmonic response of a random metasurface based on gold nano-islands in attenuated total reflectance configuration

In this work, we investigate the plasmonic response of a random metasurface based on gold nano-islands (AuNI) in an attenuated total reflectance (ATR) configuration. AuNI structures were obtained by thermal annealing of an ultrathin gold film deposited on a glass substrate. The samples exhibited a wide range of sizes and particle densities, varying the nominal gold thickness. For p polarization, a well-defined localized surface plasmon resonance (LSPR) dip was observed in all samples, while for s polarization, only AuNI with the smallest radii showed this dip. Some samples exhibited nearly zero reflection at the resonance wavelength. The highest sensitivity among all tested samples was achieved in these samples, providing potential for optimizing LSPR transducers in sensing applications. Notably, the resonance wavelength exhibited a nonlinear dependence on the refractive index in sensitivity measurements displaying a blue shift.