Simulations of high harmonic generation from plasmonic nanoparticles in the terahertz region

Abstract

Metallic nanostructures are known for enhancing weak nonlinear processes when a resonant and coherent excitation takes place. With proper structural design, an additional boost of particular nonlinear processes is expected to be possible. Here, we present a numerical technique that is capable of simulating high harmonic generation from resonantly excited metallic nanoparticles in the terahertz frequency range. We demonstrate our method by investigating the nonlinear emission of arrays of plasmonic split-ring resonators at the range of ten terahertzs. Our multiscale, non-perturbative, and microscopic approach is based on a self-consistent combination of a hydrodynamic model for the nonlinear electronic material response and the discontinuous Garlerkin time-domain technique for the evaluation of the propagation of the electromagnetic field. It is predicted that the electronic nonlinearities of plasmonic nanoparticles give rise to several harmonics in the light emission when excited by intense terahertz radiation. Furthermore, our analysis predicts a non-perturbative scaling of higher harmonics at high excitation intensities.