An ultranarrow SPR linewidth in the UV region for plasmonic sensing

Conventional surface plasmon resonance (SPR) modes based on gold and silver nanostructures only operate in the visible and near-infrared (NIR) regions. Nowadays, with the rapid development of strong coupling between molecules and plasmonic nanostructures and surface enhanced spectroscopy, it is highly desired to modulate the SPR modes with a narrow linewidth toward the ultraviolet (UV) wavelength region through a low cost and reproducible fabrication method. Herein, laser interference lithography is utilized to manufacture stable Al plasmonic arrays with well-controlled and tunable geometries. Importantly, an ultranarrow linewidth of SPR modes as narrow as 14 nm has been successfully obtained in the near UV region. The fabricated Al plasmonic arrays show a high sensitivity toward 485 nm RIU^-1 when it is used as a refractive index sensor. The results reported here make a valuable extension of plasmonic resonant modes spanning visible and NIR into the UV region, and it may provide a robust way to achieve alternative plasmonic materials for plasmon-enhanced molecular sensing, plasmonic nanolasers, non-linear optics, strong coupling and surface enhanced spectroscopy in the UV regions.