Second-harmonic generation in gold crescent- and comma-like nanostructures.

Anisotropic metal nanostructures reveal unique optical properties providing new optical effects. Here we study experimentally the nonlinear-optical response of planar arrays of gold comma-like and crescent-like nanostructures made by colloidal lithography. We show that anisotropy of the nonlinear-optical response is defined not only by the shape of the particles, but also by the relative phase of second-order susceptibility components, which are found to be spectrally sensitive. High values of circular dichroism in the second-harmonic generation response up to 70% are observed in comma-like nanostructures.