Circular motion of electromagnetic power shaping the dispersion of Surface Plasmon Polaritons

A circular zero-time- averaged power component, coupling the forward (dielectric) and backward (metal) power channels of Surface Plasmon Polaritons (SPPs), is shown to be the core ingredient for the slow-light characteristic of SPPs at the surface plasmon frequency, for both a lossless and lossy metal. Additional slow-light regimes emerging in configurations where few SPPs are strongly coupled, such as in a narrow plasmonic gap and slab, forming local extrema of the dispersion curve (branch points for positive and negative index branches), are also propelled by the circular motion of the plasmonic power. (c) 2010 Optical Society of America