Gold nanobelts as high confinement plasmonic waveguides.

Plasmon propagation in thin plasmonic waveguides is strongly damped, making it difficult to study with diffraction-limited optics. Here we directly characterize plasmon propagation in gold nanobelts with incoherent light. The data indicate a short average propagation length of 0.94 μm but also reveal a weakly excited antisymmetric mode that has a propagation length greater than 10 μm with strong confinement of 2400 nm(2). These results demonstrate that high confinement and long propagation length can be achieved with thin plasmonic structures.