Résumé
We, theoretically, show that it is possible to realize the strong coupling of a guided mode with a surface plasmon in a waveguide coated by a lossy metal. The dispersion relation of such a structure is obtained through the T-matrix algorithm combined with the the Cauchy integral technic that allows for rigorous computations of the complex poles. The strong coupling is identified by the anticrossing in the dispersion diagram and simultaneously by the crossing in the loss diagram (circular frequency vs. the imaginary part of the wave vector). The spatial structures of the different modes (original and hybridized) are computed and it is shown that spatial Rbbi oscillations appears for one of them. This last feature can be exploited to reduce losses in the propagation of surface plasmons.