Array-induced Fano resonances make high quality factors possible in plasmonic systems

We introduce the concept of array-induced Fano resonances in two-dimensional periodic arrays (metasurfaces) of plasmonic nanoparticle clusters as a mean to generate very narrow resonances despite the presence of metallic losses. We find that array-induced Fano resonances have the potential to be narrower than isolated-cluster-induced ones, and may lead to even larger field enhancements. We provide two representative examples: (i) a metasurface made of circular nanoclusters; (ii) a metasurface made of linear trimers. However, in principle the concept here introduced can be empirically extended to any cluster size and configuration. Application of array-induced Fano resonances include the improvement of sensor devices, for example.