Tailoring dispersion and eigenfield profiles of plasmonic surface lattice resonances

We investigate the radiative coupling between localized surface plasmon resonances (LSPRs) and Rayleigh anomalies (RAs) in periodic arrays of metallic nanorods with varying dimensions but equal lattice constants. The dimensions of the nanorods determine the energy and line width of the LSPR and, thus, enable tailoring of the mixed LSPR–RA states: surface lattice resonances (SLRs). We present variable angle light extinction experimental spectra for five arrays with different nanorod width and explain our results with numerical simulations. The numerical simulations are done for driven and undriven systems, with the latter revealing the SLR eigenmode properties for the first time. We provide a plane wave model that interprets the near- and far-fields of these eigenmodes, describing the intricate behavior of confinement and radiative loss versus in-plane momentum. The SLR line width, band gap associated with the coupled modes, and field extension into the surrounding dielectric are tunable via the dimensions of the nanorods.