The optical near-field of gold nanoparticle chains

We report on scanning near-field optical microscopy of one-dimensional chains of gold nanoparticles which are optically excited at their particle plasmon frequency under total internal reflection. Shape and mutual distance of the nanoparticles are tailored by lithographic fabrication. We show that the optical near-field profiles are determined by two contributions. First, the particle plasmon near-field and second, interference patterns due to the interaction of the exciting light wave and diffracted radiative grating orders.