Combining localized surface plasmons (LSPs) and diffractive surface waves (DSWs) in metallic nanoparticle gratings leads to the emergence of collective hybrid plasmonic–photonic modes known as surface lattice resonances (SLRs). These show reduced losses and therefore a higher Q factor with respect to pure LSPs, at the price of larger volumes V. By using aluminum nanoparticle square gratings with unit cells consisting of narrow–gap disk dimers (a geometry featuring a very small modal volume) we have demonstrated that an enhancement of the Q/V ratio with respect to the pure LSP and DSW is obtained for SLRs with a well–defined degree of plasmon hybridization. Simultaneously, we have reported a 5 times increase of the Q/V ratio for the gap–coupled LSP with respect to that of the single nanoparticle. The results of this work open the way toward more efficient applications for the exploitation of excitonic nonlinearities in hybrid plasmonic platforms.
Contact person: Milena De Giorgi, NANOTEC Lecce