Polarization-dependent optical excitation of gap plasmon polaritons through rectangular hole arrays

Abstract

We use variable-angle reflection ellipsometry to investigate the polarization-dependent optical excitation of highly confined gap plasmon polaritons in a fishnet metamaterial with rectangular holes. From the amplitude of features in the ellipsometric spectra and their variation with the angle of incidence, we find that the gap plasmon polaritons supported by the 35 nm thick silica gap layer are much more efficiently excited by light polarized along the short axis of holes. This inference is corroborated by numerical simulations of plasmonic near fields, while the simulated ellipsometric spectra are in excellent agreement with the measurements. By examining fishnet structures with decreasing hole sizes but a fixed aspect ratio, we find that the polarization dependence persists even in the absence of hole resonances suggesting that it can be explained by the quasi-static polarizability of holes.