Nonlocal effects investigation via the coupling between localized and acoustic plasmons

A scheme to investigate nonlocal effects in metal using the coupling between localized graphene plasmons (GPs) and acoustic plasmons (APs) is proposed. Because of the extremely strong field confinement property, the APs on a configuration consisting of monolayer graphene and a metal film have different dispersions when the nonlocal response is considered or not. A graphene nanoribbon array can effi-ciently couple incident light to the localized GPs on the ribbons and subsequently the APs. The strong coupling between the two kinds of plasmon, equivalent to electric field dipole interaction, is highly related to the acoustic plasmonic dispersion and induces different absorption spectra, depend-ing on the dispersion. Using a very simple model, nonlocal effects can be extracted from the spectra. The investigation provides a promising platform to manipulate nanophotonics and study nonlocal effects. (c) 2022 Optica Publishing Group (c) 2023 Optica Publishing Group