title: Tailoring chiro-optical effects by helical nanowire arrangement.
abstract: In this work, we experimentally investigate the chiro-optical properties of 3D metallic helical systems at optical frequencies. Both single and triple-nanowire geometries have been studied. In particular, we found that in single-helical nanostructures, the enhancement of chiro-optical effects achievable by geometrical design is limited, especially with respect to the operation wavelength and the circular polarization conversion purity. Conversely, in the triple-helical nanowire configuration, the dominant interaction is the coupling among the intertwined coaxial helices which is driven by a symmetric spatial arrangement. Consequently, a general improvement in the g-factor, extinction ratio and signal-to-noise-ratio is achieved in a broad spectral range. Moreover, while in single-helical nanowires a mixed linear and circular birefringence results in an optical activity strongly dependent on the sample orientation and wavelength, in the triple-helical nanowire configuration, the obtained purely circular birefringence leads to a large optical activity up to 8°, independent of the sample angle, and extending in a broad band of 500 nm in the visible range. These results demonstrate a strong correlation between the configurational internal interactions and the chiral feature designation, which can be effectively exploited for nanoscale chiral device engineering.
authors.affiliation: CNR NANOTEC - Istituto di Nanotecnologia, Polo di Nanotecnologia, c/o Campus Ecotekne, via Monteroni, 73100 Lecce, Italy. vittorianna.tasco@nanotec.cnr.it and Universitaà del Salento Dip. Mat-Fis Ennio De Giorgi, I-73100 Lecce, Italy.
authors.forename: Marco
authors.initials: M
authors.lastname: Esposito
authors.affiliation: CNR NANOTEC - Istituto di Nanotecnologia, Polo di Nanotecnologia, c/o Campus Ecotekne, via Monteroni, 73100 Lecce, Italy. vittorianna.tasco@nanotec.cnr.it.
authors.forename: Vittorianna
authors.initials: V
authors.lastname: Tasco
authors.affiliation: CNR NANOTEC - Istituto di Nanotecnologia, Polo di Nanotecnologia, c/o Campus Ecotekne, via Monteroni, 73100 Lecce, Italy. vittorianna.tasco@nanotec.cnr.it.
authors.forename: Francesco
authors.initials: F
authors.lastname: Todisco
authors.affiliation: Universitaà di Roma La Sapienza, Dip. SBAI, via Scarpa 16, 00161 Roma, Italy.
authors.forename: Alessio
authors.initials: A
authors.lastname: Benedetti
authors.affiliation: Universitaà del Salento Dip. Mat-Fis Ennio De Giorgi, I-73100 Lecce, Italy.
authors.forename: Iolena
authors.initials: I
authors.lastname: Tarantini
authors.affiliation: CNR NANOTEC - Istituto di Nanotecnologia, Polo di Nanotecnologia, c/o Campus Ecotekne, via Monteroni, 73100 Lecce, Italy. vittorianna.tasco@nanotec.cnr.it.
authors.forename: Massimo
authors.initials: M
authors.lastname: Cuscunà
authors.affiliation: CNR NANOTEC - Istituto di Nanotecnologia, Polo di Nanotecnologia, c/o Campus Ecotekne, via Monteroni, 73100 Lecce, Italy. vittorianna.tasco@nanotec.cnr.it.
authors.forename: Lorenzo
authors.initials: L
authors.lastname: Dominici
authors.affiliation: CNR NANOTEC - Istituto di Nanotecnologia, Polo di Nanotecnologia, c/o Campus Ecotekne, via Monteroni, 73100 Lecce, Italy. vittorianna.tasco@nanotec.cnr.it.
authors.forename: Milena
authors.initials: M
authors.lastname: De Giorgi
authors.affiliation: CNR NANOTEC - Istituto di Nanotecnologia, Polo di Nanotecnologia, c/o Campus Ecotekne, via Monteroni, 73100 Lecce, Italy. vittorianna.tasco@nanotec.cnr.it.
authors.forename: Adriana
authors.initials: A
authors.lastname: Passaseo