Second harmonic generation in periodical metal-insulator-metal nanoparticle arrays

The collective oscillation of free electrons in metals (plasmon) leads to a localized field enhancement at the surface. Structures with periodically arranged metallic nano-particles possess two plasmonic resonances: one from the individual nano-particles (localized surface plasmon resonance, LSPR) and one from the collective response triggered by the periodic arrangement (surface lattice resonance, SLR) [1]. Whereas the LSPR is fixed by the sample geometry, the spectral position of the SLR is tuneable with the optical angle of incidence. Both the resonances as well as plasmonic nano-gaps are associated to a strong field enhancement, which can boost nonlinear optical effects.