Ricerc@Sapienza

Semiconductor nanowires made of high refractive index materials can couple the incoming light to specific waveguide modes that offer resonant absorption enhancement under the bandgap wavelength, essential for light harvesting, lasing and detection applications. Moreover, the non-trivial ellipticity of such modes can offer near field interactions with chiral molecules, governed by near chiral field. These modes are therefore very important to detect.

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