Nanoscale 3D Chiral Plasmonic Helices with Circular Dichroism at Visible Frequencies

作者：Esposito, Marco^*; Tasco, Vittorianna; Cuscuna, Massimo; Todisco, Francesco; Benedetti, Alessio; Tarantini, Iolena; De Giorgi, Milena; Sanvitto, Daniele; Passaseo, Adriana

来源：ACS Photonics, 2015, 2(1): 105-114.

DOI：10.1021/ph500318p

• 3D chirality
• focused ion and electron beam induced deposition
• nanophotonics
• 3D proximity effect compensation
• plasmonic metamaterial
• circular dichroism

The nanoscaling of metamaterial structures represents a technological challenge toward their application in the optical frequency range. In this work we demonstrate tailored chiro-optical effects in plasmonic nanohelices, by a fabrication process providing a nanometer scale control on geometrical features, that leads to a fine tuning of operation band even in the visible range. Helicoidal 3D nanostructures have been prototyped by a bottom-up approach based on focused ion and electron beam induced deposition, investigating resolution limits, growth control and 3D proximity effects as a function of the interactions between writing beam and deposition environment. The fabricated arrays show chiro-optical properties at the optical frequencies and extremely high operation bandwidth tailoring dependent on the dimensional features of these 3D nanostructures: with the focused ion beam we obtained a broadband polarization selection of about 600 nm and maximum dissymmetry factor up to 40% in the near-infrared region, while with the reduced dimensions obtained by the focused electron beam a highly selective dichroic band shifted toward shorter wavelengths is obtained, with a maximum dissymmetry factor up to 26% in the visible range. A detailed finite difference time domain model highlighted the role of geometrical and compositional parameters on the optical response of fabricated nanohelices, in good agreement with experimental results.

• 出版日期2015-1