Surface plasmon polaritons in sub-wavelength metallic gratings studied by higher-order angle-resolved spectroscopy

Angle-resolved reflection spectroscopy is used to study surface plasmon polariton modes of metallic gratings consisting of sub-wavelength grooves. The used optical set-up allows recording of zero and m = -1 order reflection spectra in the visible and near infra-red spectral region. The different modes and their mutual coupling was identified in the dispersion diagram by means of modal theory. Surface plasmon modes at the grating surface and cavity modes in the sub-wavelength grooves were evidenced.