Surface plasmon scattering by shallow and deep surface defects

Surface plasmon scattering by 1D indentations and protrusions is examined, mainly in the optical regime. The width of the defects is fixed, while its height is varied. Both individual and arrays of defects are considered. Protrusions mainly reflect the incident plasmons in the optical range. Indentations mainly radiate the incident plasmon out of plane. An indentation produces maximum reflections and out-of-plane radiation at the same wavelength, when its interaction with the incident surface plasmon is resonant. Protrusions, in general, exhibit maximum reflection and radiation at different wavelengths. Shallow arrays of either defects produce a photonic band-gap, whose spectral width can be broadened by increasing the defects height or depth. At wavelengths inside the bandgap ridge arrays reflect SPPs better than groove arrays, while groove arrays radiate SPPs better than ridge arrays.