Oral: Harnessing Nonlinear Light: Exploring Plasmonic Nanoparticles for Amplification, Frequency Conversion, and Terahertz Emission

We explore nonlinear optical behavior of plasmonic metal nanoparticles (MNPs) using finite-difference time-domain (FDTD) simulations coupled with hydrodynamic descriptions for electrons and theoretical modeling. Specifically, we explore parametric amplification, spontaneous parametric down conversion (SPDC) and terahertz (THz) emission. For parametric amplification and SPDC, we investigate the difference-frequency generation (DFG) in L-shaped MNP arrays, focusing on intrinsic plasmonic nonlinearity. It reveals that significant yield is achievable on the scale of just tens of nanometers from MNP only without any need for nearby nonlinear materials. We further examine the generation of THz from MNPs with C₂ᵥ symmetry in three configurations: L-shaped, crescent-shaped, and pi-shaped split-ring resonators. It shows how symmetry influences the plasmonic modes and higher-order resonances. Using our FDTD simulations, we analyze both second harmonic generation (SHG) and broadband THz emission through DFG with pulsed excitation. Results highlight the role of symmetry in determining polarization states and nonlinear optical responses. Together, these works provide new insights into nonlinear processes, plasmonic resonances, and symmetry, with broad applications in spectroscopy, nanophotonics, and optoelectronics.