Thermosensitive Plasmonic Color Enabled by Sodium Metasurface

Active plasmonic nanostructures have attracted tremendous interest in nanophotonics and metamaterials owing to the dynamically switchable capabilities of plasmonic resonances. In this study, tunable hybrid plasmon resonances (HPR) of sodium metasurfaces through heat-initiated structural transformation is experimentally demonstrated. A HPR is formed by coupling surface plasmon polaritons (SPP) and gap plasmon resonances (GPR), whose resonant wavelengths are highly sensitive to gaseous nanogaps. By carefully manipulating the thermo-assisted spin-coating process and post-thermal treatment, tuning of the HPR is achieved because of the phase transition between the antidome and nanodome structural profiles of liquid sodium inside the patterned fused silica substrates. Furthermore, the figure of merit of the heat initiated variable structure-spectrum is demonstrated that is highly dependent on the size of the substrate patterns, based on which temperature-sensitive plasmonic color and “invisible ink” of sodium metasurfaces are demonstrated. These findings can lead to new solutions for manipulating low-cost and high-performance active plasmonic devices.