Linear and nonlinear optical characterization of Au/Si3N4 multilayer metamaterials

Light manipulation at the nanoscale is a fundamental challenge for the development of advanced light sources as single-photon sources or nanolasers. Consequently, the design and fabrication of novel nanostructured materials able to satisfy this demand has become of paramount importance in nanophotonics. In recent years there has been an exponential growth in the research on the properties of optical metamaterials, i.e. artificially nanostructured materials whose optical functionalities can be engineered by properly controlling the features and the coupling of the structural nanometric building-blocks on a sub-wavelength scale. The aim of this thesis is the synthesis and characterization of the linear and nonlinear optical properties of plasmonic multilayer hyperbolic metamaterials obtained by combining and nanostructuring in one dimension a metal and a dielectric. In particular the study will focus on the development and the description of plasmonic metamaterials constituted by alternating layers of gold (Au) and silicon nitride (Si3N4). A set of multilayer hyperbolic metamaterials will thus be realized tuning their epsilon near-zero wavelength in order to obtain enhanced nonlinear optical properties at accurately selected spectral positions. In this thesis work, the optical Kerr effect will be studied in the picosecond excitation regime in the visible and near-infrared spectral range. The crafted plasmonic metamaterial exhibits a remarkable nonlinear behavior at its epsilon near-zero wavelength that was not previously observed in its constituent materials, thus completely owing its nonlinear response to the nanoscale combination of Au and Si3N4.