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.
We report a comparative experimental and theoretical study of second harmonic generation from a 20nm-thick indium tin oxide nanolayer in the proximity of the epsilon-near-zero condition. We record the efficiency of the second harmonic signal both as a function of wavelength as well as of the angle of incidence around the epsilon-near-zero crossing point. We compare our experimental results with numerical simulations based on a hydrodynamical model able to capture all major physical mechanisms driving the electrodynamic behavior of conductive oxide layers, with unique aspects of the different nonlinear sources. We found a very good quantitative and qualitative agreement between experiment and theory.
We demonstrate second harmonic generation from a GaAs substrate, well-below the absorption edge. The pump is tuned in the transparency range, at 1064 nm, while the SH is tuned in the opaque spectral range of GaAs, at 532 nm. We work far from the phase matching condition and we find that the phase locked component of the second harmonic propagates trough the opaque material. As expected, we find that the polarization of the generated SH signal is sensitive to the polarization of the pump. We demonstrate different surface and bulk contributions to the SH transmitted signal and we show that the surface-generated SH components can be more intense than bulk-generated SH signals. The experimental results are contrasted with numerical simulations that include these two factors, using a hydrodynamic model, accounting for all aspects of the dynamics, including surface and bulk generated harmonic components.