Nonlinear detection of third harmonic generation (THG) in gold metamaterial

Abstract

This report investigates the optical nonlinearity in thin gold film metasurfaces with an aperture array to realize third harmonic generation (THG). Using Lumerical finite difference time domain (FDTD), nonlinear third harmonic generation was simulated and compared to previous reported works on nonlinear scattering theory. The proposed FDTD nonlinear simulation is computational friendly, simple and provides a good case study when considering the effect of higher excitation power on metamaterials to realise THG, as compared to past simulations carried out that involves importing data from Lumerical FDTD to Matlab to carry out the nonlinear scattering calculation to obtain the final result. The conversion efficiency (the ratio of THG power to the excitation power) of three different aperture arrays was obtained with results showing that the H-shape array would give the highest conversion efficiency of about 0.52 %. The result shows that the FDTD nonlinear simulation approach used agrees with the experimental result and nonlinear scattering theory. This project points towards an effective detection of third harmonic generation (THG) from thin plasmonic metal films using the finite difference time domain (FDTD) method.