Surface electromagnetic modes (surface plasmons) of lamellar metallic gratings with very narrow and deep grooves [1] or slits [2] are reviewed from the theoretical point of view. In the reflection configuration [1] we will show how there are basically two kind of modes: surface plasmon polaritons (SPPs) and waveguide resonances in which light is strongly localized inside the grooves. Experimental evidence of the excitation of these two kind of plasmons in the optical regime is also given. In the transmission configuration [2], transmission resonances associated to the excitation of surface plasmons of the grating can appear in the spectrum. We will show that there are two possible ways of transferring light from the upper surface to the lower one: by the excitation of coupled SPPs on both surfaces or by the coupling of the incident light with waveguide resonances located in the slits. Both mechanisms can lead to almost perfect transmittance for those particular wavelengths.
[1] T. Lopez-Rios, D. Mendoza, F.J. Garcia-Vidal et al., Phys. Rev. Lett. 81, 665 (1998).
[2] J. A. Porto, F. J. Garcia-Vidal and J. B. Pendry, Phys. Rev. Lett. 83, 2845 (1999).