Second-Harmonic Generation in Plasmonic Nanostructures

Abstract Nonlinear plasmonics is a bridge linking the conventional nonlinear optical com- ponents with the contemporary nanoptics. At optical frequencies, metals support surface electromagnetic modes —surface plasmon-polaritons — that have the ability to localize light far below the diffraction limit, down to sub-wavelength regions. This unique property can be exploited to enhance inherently weak nonlinear light-matter interactions. In this thesis, we present numerical study of second-harmonic genera- tion (SHG) in distinct plasmonic structures. A part of this thesis comprises the study of SHG in hybrid plasmonic nanopatch antennas. Exploiting the localized modes (field enhancements) of the nanopatch system, we demonstrate that the nonlinearities arising from spacer layer of the nanopatch system can be greatly enhanced. The presented study enables an efficient and technologically competitive route to real- ize nanophotonics devices like onchip frequency converter and optical bistability. Plasmonic Waveguides provide an integrated platform to develop efficient nanoscale ultrafast photonic devices. In this context, second part of the thesis presents a novel semi-analytical method to study SHG from plasmonic and/or photonic waveguides with nonlinearities of its constituents modeled using the “Hydrodynamic Theory of free electrons”. Nonlocal optical effects, arising due to plasma gas nature of elec- trons in the media like metal, significantly alter the optical response of the system, especially, at the sizes much smaller than the incidence of radiation. Our proposed method, thus, allows the studies in the presence of additional degrees of freedom and their implications.