Nonlinear optical enhancement caused by a higher order multipole mode of metallic triangles†
Abstract
We describe a nonlinear optical study of gold triangles that exploits a higher order plasmonic resonance. A comprehensive nonlinear optical characterisation was performed both by second harmonic generation (SHG) and two photon fluorescence spectroscopy (2PF). We demonstrate and explain the enhancement of the coherent and incoherent nonlinear optical emission by a higher order multipolar mode of the plasmonic structure. The peculiarities of the mode shape and its influence on intensity and polarisation of the nonlinear signal are experimentally and numerically confirmed.