Enhanced photo-induced optical activity of crisscrossed self-organized gratings in photosensitive nanolayers by introducing bi-periodicity

In the present work, the enhancement of photoinduced optical activity in a photosensitive nanolayer of AgCl doped by Ag nanoparticles, using bi-periodic crisscrossed self-organized periodic nanostructures (C-SPNs) is achieved. We found that the formation of two non-identical SPNs (i.e., with different periods), which crisscrossed each other, enhances the rotation of the polarization plane of the linear polarized probe beam, compared to the case when the two nanostructures are identical (i.e., having the same period). The difference in periods of the two C-SPNs increases the anisotropy of the medium, which in turn boosts the optical chirality produced by the formation of complex crisscrossed gratings made of Ag nanoparticles. The angle between the two gratings can be a control parameter for the amount and sign of rotation of the polarization plane of the probe beam. The enhanced optical activity of the bi-periodic C-SPNs, compared to the identical C-SPNs, can be attributed to the formation of more intricate chiral building blocks at the intersections of the two gratings.