Collective plasmonic oscillations in nanostrips arrays and sine wave gratings. Comparative study

Excitation of collective plasmonic modes and their effects on optical behavior were experimentally and theoretically studied in 1 D arrays of gold nanostrips in comparison with those in continuous gold films with a sine wave profile and similar periodicity. Two kinds of collective resonance modes are efficiently excited in gold strips, with participation of gold -air and gold- glass interfaces. These modes correspond to maxima in the angular dependence of reflection, as opposed to minima observed at surface plasmon polariton conditions in a continuous sine wave grating. Spectral and polarization dependences are obtained. A theoretical approach based on the novel combined transfer-matrix coupled-wave analysis and coordinate transformation method is shown to well describe experiments.