Asymmetric transmission of the surface plasmon polaritons in diffractive plasmonic structures

We have shown that a square array of scatterers deposited on a metal surface in a triangular mesh to which a diffractive structure is added to the left side reveals asymmetric transmission of surface plasmon polaritons. This asymmetric transmission of a surface plasmon polariton does not require either electrical nonlinearity or the presence of a magnetic field but is a consequence solely of the geometry of the structure. The mechanism for this property is related to the higher Bragg modes that are excited due to the diffractive structure. To study the reflectivity and transmissivity for both the periodic and diffractive structures we used a multiple-scattering approach in which the response of the individual scatterer to the incident field is described by its isotropic dipolar polarizability. The underlying mechanism of asymmetric transmission is described in terms of a simple analytical model which allows to identify propagating higher Bragg modes.