Enhanced second harmonic generation of gold nanostars: optimizing multipolar radiation to improve nonlinear properties.

ABSTRACT

We report a detailed investigation on the second harmonic generation (SHG) emission from single 150 nm diameter non-centrosymmetric gold nanoparticles. Polarization-resolved analysis together with scanning electron microscopy images shows that these nanostructures exhibit a unique polarization-sensitive SHG that depends strongly on the particle's shape. An analytical approach based on multipolar analysis is introduced to link SHG properties to the nanoparticles' shape. Those multipolar modes can be probed using polarization-resolved SHG. This multipolar analysis offers a physical picture of the relation between shape (size, symmetries, defects, etc.) and nonlinear polarized optical efficiency.