Channel plasmon-polaritons: modal shape, dispersion, and losses
  We theoretically study channel plasmon-polaritons (CPPs) with a geometry similar to that in recent experiments at telecom wavelengths (Bozhevolnyi et al., Nature 440, 508 (2006)). The CPP modal shape, dispersion relation, and losses are simulated using the multiple multipole method and the finite difference time domain technique. It is shown that, with the increase of the wavelength, the fundamental CPP mode shifts progressively towards the groove opening, ceasing to be guided at the groove bottom and becoming hybridized with wedge plasmon-polaritons running along the groove edges. 
Esteban Moreno, F. J. Garcia-Vidal, Sergio G. Rodrigo, L.   Martin-Moreno, Sergey I. Bozhevolnyi