Ricerc@Sapienza

Optical enantioselectivity of chiral molecules could be enhanced by depositing them on suitable nanostructured substrates. Different kind of chiral substrates can be developed, but chiral features are in general difficult to fabricate or costly. Self-assembled approach allows realizing plasmonic metasurfaces with a low cost reliable procedure. In this case asymmetric fabrication parameters can induce chiral optical response of the realised substrate. Self-organized polystyrene spheres deposited on glass substrate, are utilised to produce asymmetric hole array on a metal thin film.

We report on the extrinsic chirality behavior of GaAs-based NWs asymmetrically
hybridized with Au. The samples are fabricated by a recently developed,
lithography-free self-organized GaAs growth, with the addition of AlGaAs shell and
GaAs supershell. The angled Au flux is then used to cover three-out-of-six sidewalls
with a thin layer of Au. Oblique incidence and proper sample orientation can lead
to circular dichroism. We characterize this chiral behavior at 532 nm and 980 nm

Optical circular dichroism (CD) is an important phenomenon in nanophotonics, that addresses top level applications such as circular polarized photon generation in optics, enantiomeric recognition in biophotonics and so on. Chiral nanostructures can lead to high CD, but the fabrication process usually requires a large effort, and extrinsic chiral samples can be produced by simpler techniques. Glancing angle deposition of gold on GaAs nanowires can (NWs) induces a symmetry breaking that leads to an optical CD response that mimics chiral behavior.