Anisotropy versus circular dichroism in second harmonic generation from fourfold symmetric arrays of G-shaped nanostructures

Circular dichroism in optical second harmonic generation (CD-SHG) is studied in planar symmetrical arrays of G-shaped and mirror-G-shaped nanostructures. Anisotropic CD-SHG measurements demonstrate a strong dependence of the value and the sign of the CD effect on the angle of incidence of the fundamental radiation. We show that both dipole and higher order multipole components of the second order susceptibility are responsible for the CD response from G-shaped nanostructures.