Efficient spectral domain Green´s function analysis of novel metamaterial bandgap guiding structures

The Green´s function analysis of oversized waveguides with one wall realized as a periodic structure is presented in this paper. Two different realizations of the periodic structures were considered: the bed-of-nails surface and the mushroom surface. Since the period of these surfaces is small compared to wavelength it is possible to take advantage of the asymptotic boundary conditions in the derivation of the required Green´s functions. By doing so, we avoid the usual Floquet mode approach needed in the analysis of periodic surfaces and significantly reduce the overall numerical complexity. The Green´s functions developed in this way allow dispersion and electromagnetic field analysis since their poles correspond to surface wave modes and waveguide modes. These results reveal the dispersion characteristics of the observed structures and the bandwidth usable in the waveguide applications. The computed results are compared with the results obtained with a general electromagnetic solver and the agreement is very good.