Harmonic generation from gold nanolayers: bound- and hot-electron contributions

Currently, nanostructures are routinely fabricated and integrated in different photonic devices for a variety of purposes and applications. For instance, in order to engineer properly nano-antennas or filters, it is important to understand accurately how light interacts with metals, semiconductors, or ordinary dielectrics at the nanoscale. When the nanoscale is reached, light-matter interactions displays new phenomena and conventional approximations may not always be applicable. Thus, new strategies must be sought in order to study and understand light-matter interactions at the nanoscale. In this work, we present experimental results of second and third harmonic generation from gold nanolayers, raveling novel behavior at nanoscale. These measurements are compared with numerical simulations based on a microscopic hydrodynamic model which accounts for surface, magnetic and bulk nonlinearities arising from both free and bound charges, preserving linear and nonlinear dispersion, nonlocal effects due to pressure and viscosity, and an intensity dependent free electron density, to which we refer as hot electrons contribution.