Multipolar second-harmonic generation in noble metal nanoparticles

Second-harmonic generation from noble metal nanoparticles with a noncentrosymmetrical shape is theoretically investigated by using finite element method simulations. The relative weight of the dipolar and quadrupolar responses is investigated in terms of both light polarization and size dependence of the harmonic scattered intensity. It is shown that, even for small deformations as compared with purely spherical particles, the dipolar response dominates and scales as the nanoparticle surface area squared. The difference between gold and silver metal nanoparticles is also addressed.