Tunable Plasmonic System Based on Disordered Palladium Nanoparticles and Its Application to Optical Hydrogen Sensors

Plasmonic systems based on metallic nanostructures have special properties for light localization, photon transportation, and energy harvesting and have been widely applied in various optical applications. Here, we propose a tunable plasmonic system composed of disordered palladium (Pd) nanoparticles (NPs) on a planar optical cavity. We manipulate optical absorption intensity and bandwidth by controlling the effective thickness of the Pd NPs, which achieve an ultralow reflectance of 0.06%. Furthermore, the optical absorption mode of the plasmonic system can be modulated by the hydrogen absorption of the Pd NPs. The tunable optical absorption of the plasmonic system can be explained by the coupled-mode theory. This Pd-based plasmonic system will not only facilitate a further understanding of the optical properties of disordered systems but also provide a novel platform for practical applications such as visual hydrogen sensing.