Optical characterisation of plasmonic nanostructures on planar substrates using second harmonic generation

Polarization dependent second{harmonic generation (SHG) measurements were performed ex situ on plasmonic nanostructures grown by self{assembly on nanopatterned templates. These exploratory studies of Ag nanoparticles show that SHG is highly sensitive to the local elds associated with the morphology of the NP layer, with the substrate making little or no contribution. The anisotropic polarized SH response is easily detected under non{resonant conditions and shows promise as a complementary technique for the in situ characterization of anisotropic nanoparticle arrays. In particular, the ratio of two parameters related to the p{polarized SH response arising from p{ and s{polarized excitation showed over an order of magnitude difference between isotropic and anisotropic NPs. While these measurements involved rotating the sample to access orthogonal azimuths, the results show that a simple xed normal incidence geometry could be used for in situ measurements of mirror plane symmetry breaking, associated with anisotropic nanostructure morphology, in situations where rotating the sample may be neither desirable nor easily accomplished.