Analysis of the Bloch mode spectra of surface polaritonic crystals in the weak and strong coupling regimes:: grating-enhanced transmission at oblique incidence and suppression of SPP radiative losses

The Bloch mode spectrum of surface plasmon polaritons (SPPs) on a finite thickness metal film has been analyzed in the regimes of weak and strong coupling between SPP modes on the opposite film interfaces. The SPP mode dispersion and associated field distributions have been studied. The results have been applied to the description of the light transmission through thick and thin periodically structured metal films at oblique incidence. In contrast to normal incidence, all SPP Bloch modes on a grating structure participate in the resonant photon tunnelling leading to the transmission enhancement. However, at the angle of incidence corresponding to the crossing of different symmetry film SPP Bloch modes, the far-field transmission is suppressed despite the enhanced near-field transmission. The combined SPP mode consisting of the two film SPPs having different symmetries that is achieved at the crossing frequency exhibits no radiative losses on a structured surface. (C) 2004 Optical Society of America.