Nonlinearity Assisted Mie Scattering from Nanoparticles

Scattering by nanoparticles is an exciting branch of physics to control and manipulate light. More specifically, there have been fascinating developments regarding light scattering by sub-wavelength particles, including high-index dielectric and metal particles, for their applications in optical resonance phenomena, detecting the fluorescence of molecules, enhancing Raman scattering, transferring the energy to the higher order modes, sensing and photodetector technologies. It recently gained more attention due to its near-field effect at the nanoscale and achieving new insights and applications through space and time-varying parametric modulation and including nonlinear effects. When the particle size is comparable to or slightly bigger than the incident wavelength, Mie solutions to Maxwell's equations describe these electromagnetic scattering problems. The addition and excitation of nonlinear effects in these high-indexed sub-wavelength dielectric and plasmonic particles might improve the existing performance of the system or provide additional features directed toward unique applications. In this thesis, we study the Mie scattering from dielectric and plasmonic particles in the presence of nonlinear effects. For dielectrics, we present a numerical study of the linear and nonlinear diffraction and focusing properties of dielectric metasurfaces consisting of silicon microcylinder arrays resting on a silicon substrate. Upon diffraction, such structures lead to the formation of near-field intensity profiles reminiscent of photonic nanojets and propagate similarly. Our results indicate that the Kerr nonlinear effect enhances light concentration throughout the generated photonic jet with an increase in the intensity of about 20% compared to the linear regime for the power levels considered in this work. The transverse beamwidth remains subwavelength in all cases, and the nonlinear effect reduces the full width. In the future, we want to optimize the performance through parametric modification of the system and continue our study with plasmonic structures in time–varying scenarios. We hope that with appropriate parametric modulation, intermodal energy transfer is possible in such structures. We want to explore the nonlinear excitation to transfer energy in higher-order modes by exploiting different wave-mixing interactions in time-modulated scatterers.