“…In the interaction of light with nanostructures many intricate effects can be observed. For light with high local intensities also nonlinear effects, such as second harmonic generation (SHG), can be observed [1,2]. In plasmonic nanostructures, which are most often created from gold, silver or aluminium, collective oscillations of the free electron density (so-called localized surface plasmon polaritons) are excited, leading to high scattering and absorption cross-sections, a high local concentration of optical energy near the nanostructures, strong electric near-fields, and resonances that depend on the geometry, material, arrangement, and dielectric environment [3,4].…”