Harmonic generation in metal-insulator and metal-insulator-metal nanostructures

Abstract

We report that the second and third harmonic signal reductions with insulator film surface coverage over a gold substrate gives a measure of the electron density in the spill out volume of the insulator, which is dubbed metal insulator gap states. For metal-insulator-metal (MIM) structures we observe enhancement saturation and quenching of the third harmonic efficiencies well above the efficiencies for metal-insulator (MI) samples. The measured optical harmonics of scattered light from MI and MIM systems are compared with detailed simulations of the nonlinear interactions including free electron spill out into the insulator, nonlocal and electron quantum tunneling effects. Gold coated substrates are covered with variable thin insulator film thicknesses using atomic layer deposition. Optical harmonics of light scattered from two insulator materials (ZnO and Al2O3) are measured in our experiments. Based on our simulations we conclude that the observed MIM signal enhancement effects are primarily due to nonlocal phenomena in an electron gas.We present additional, detailed information about our simulations and experiments in this supplement.

Inch-Scale Ball-in-Bowl Plasmonic Nanostructure Arrays for Polarization-Independent Second-Harmonic Generation

“…Strong field enhancements occur within nanoscale gaps between metal particles and metal mirrors of MDM structures, which support both Fabry–Pérot resonance mode and SPR mode. , Two spatially overlapped resonance modes can be tuned to the fundamental and the second-harmonic wavelength by changing the size and gap length of nanostructures, which results in the maximization overlap in frequency region. To date, several studies have been carried out to build proof-of-concept samples based on MDM nanostructures and confirm its efficient application in SHG. ,− …”