Abstract
Optical Second Harmonic Generation (SHG) is obtained from adsorbed gold nanoparticles with an average diameter of 16 nm at the air / aqueous solution interface in reflection. A detailed analysis of the depth profile of the SHG intensity detected shows that two contributions appear in the overall signal, one arising from the air / aqueous solution interface that is sensitive to the gold nanoparticles surface excess and one arising from the bulk aqueous phase. The latter is an incoherent signal also known as Hyper Rayleigh scattering. The results are in agreement with an analysis involving Gaussian beam propagation optics and Langmuir isotherm. It also reveals discrepancies for the largest concentrations used and proposes a new route for the design of soft metasurfaces.