Surface plasmon interferometry: measuring group velocity of surface plasmons

Optical transmission spectroscopy on metal films with slit-groove pairs is conducted. Spectra of the light transmitted through the slit exhibit Fabry-Perot-type interference fringes due to surface plasmons propagating between the slit and the groove. The spectral dependence of the period of interference fringes is used to determine the group velocity of surface plasmons on flat gold and silver surfaces. (c) 2007 Optical Society of America.