Fano resonance boosted cascaded optical field enhancement in a plasmonic nanoparticle-in-cavity nanoantenna array and its SERS application

摘要

A nanoantenna array of plasmonic nanoparticles in nanocavities whose cascaded field enhancement is boosted by Fano resonance has been made. The resonance originates from the strong coupling between a dark mode of the 20-nanometre gold nanoparticle and a high-order bright mode of the 120-nanometre gold nanocavity. Scientists from Tsinghua University in Beijing, China, made these nanostructures by using a cost-effective, efficient and reliable nanofabrication technique involving room-temperature nanoimprinting lithography and anisotropic reactive ion etching. The method ensures that only one nanoparticle is formed in each cavity, which is important since the number of nanoparticles can greatly affect the cascaded field enhancement. The researchers demonstrated the potential of these nanostructures by using as a substrate for surface-enhanced Raman spectroscopy and realizing an enhancement factor of 2 × 107 for the detection of 4-aminothiophenol molecules.