Wedge geometry of photosensitive nanolayers enhances induced optical gyrotropy

Intersecting gratings are generated in wedge-shaped photosensitive AgCl-Ag thin films through double exposure to a linearly polarized He-Ne laser beam, resulting in crisscrossed nanostructures with significant optical gyrotropy within the visible spectrum. Our findings reveal that the optical rotation generated by two intersecting gratings is substantial, with a maximum rotation of approximately 5°. This effect is notably enhanced when the AgCl layer is shaped as a wedge, achieving a maximum rotation of around 9°. This is particularly impressive for a photonic material with a thickness of only 60 nm. A low-power He-Ne laser sequentially exposes a wedge-shaped Ag/AgCl/glass system to create intricate nanostructures. The wedge geometry enables multiple gratings with different periods, determined by interference with the excited TE₀mode. This arrangement of intersecting gratings increases the medium's anisotropy, enhancing optical chirality. The angle between the laser polarization vectors is key, controlling both the direction and magnitude of the induced optical rotation.