Papers by Marina Giordano
2014 Third Mediterranean Photonics Conference, 2014
ABSTRACT Here we report on the potentiality of the self-organised nanopatterning in view of broad... more ABSTRACT Here we report on the potentiality of the self-organised nanopatterning in view of broadband photon harvesting in thin film amorphous silicon (a-Si) solar cells. Self-organised pattern formation of glass, semiconductor and TCO interfaces is achieved recurring to low-energy Ion Beam Sputtering (IBS).
Journal of the European Optical Society: Rapid Publications, 2012
ABSTRACT Here we investigated the asymmetric transmission and the anomalous refraction introduced... more ABSTRACT Here we investigated the asymmetric transmission and the anomalous refraction introduced by a metasurface of bent gold nanowires. The refraction follows the generalized Snell’s law that takes into account the resonant behavior of metallic nanostructures located at the interface between two dielectrics. Measurements performed in the linear optical regime reveal a large sensitivity to the subwavelength features of the gold nanostructures.
Photonics Letters of Poland, 2013
Advanced Optical Materials, 2013
We report on the interaction of localized surface plasmon resonances (LSPRs) with the photonic mo... more We report on the interaction of localized surface plasmon resonances (LSPRs) with the photonic modes in an opal photonic crystal. Gold nanocrescents have been evaporated at glancing angles both over microsphere monolayers and artificial opals. Microsphere monolayers allow us to identify the three localised plasmonic resonances observed in the nanocrescent optical spectra. By changing the microsphere diameter, the opal photonic stop band and a selected plasmonic resonance can be spectrally overlapped causing a dramatic change of the properties of both excitations. We observe the creation of new modes whose spectral position and dispersion properties are a combination of those localised in nanoparticle plasmons and in the photonic crystal. Submitted to 2 42
The Journal of Physical Chemistry C, 2014
Since its discovery, surface-enhanced Raman spectroscopy (SERS) has pushed researchers' interest ... more Since its discovery, surface-enhanced Raman spectroscopy (SERS) has pushed researchers' interest to develop different kinds of active substrates for high sensitivity molecular detection. Defocused ion beam sputtering (IBS) represents a viable route for the production of large scale, highly reproducible SERS-active substrates consisting of near-field coupled nanowires featuring localized surface plasmon resonances in the visible and the near-infrared. Here we investigate the field enhancement and spatial confinement in the visible and the near-infrared of arrays of optically resonant gold nanowires, using two complementary techniques: SERS and scanning near-field optical microscopy (SNOM). While SERS allows us to quantify the field enhancement factor, SNOM is used to image the localization of the enhanced electromagnetic fields. We show that in the visible (633 nm) the nanowires are SERS active only for excitation polarized parallel to the wire-to-wire nanocavities, yielding enhancement factors of 7 × 10 3 . In the near-infrared (785 nm) we observe a 2-fold larger SERS enhancement (1.3 × 10 4 ) for excitation parallel to the nanocavities and detect the onset of SERS amplification for excitation polarization parallel to the nanowires long axis. Polarization-sensitive SNOM in the near-infrared (830 nm) enables the correlation of the scattered intensity with the sample morphology at the local scale. We demonstrate that the field enhancement stems from the wire-to-wire nanocavity regions when the excitation field is polarized parallel to the wire-to-wire nanocavity, while we observe more complex field confinement patterns related to the partially inhomogeneous morphology of the substrate when the polarization is parallel to the nanowires long axis. Our experiments strongly suggest IBS-fabricated nanowires as novel substrates for plasmon-enhanced spectroscopies.
Physical Review Letters, 2011
Here we report the experimental observation of circular dichroism in the second-harmonic field (8... more Here we report the experimental observation of circular dichroism in the second-harmonic field (800-400 nm conversion) generated by self-organized gold nanowire arrays with subwavelength periodicity (160 nm). Such circular dichroism, raised by a nonlinear optical extrinsic chirality, is the evident signature of the sample morphology. It arises from the curvature of the self-assembled wires, producing a lack of symmetry at oblique incidence. The results were compared, both in the optical linear and nonlinear regime, with a reference sample composed of straight wires. Despite the weak extrinsic optical chirality of our samples (not observable by our optical linear measurements), high visibility (more than 50%) was obtained in the second-harmonic generated field.
Optics Express, 2013
Gold nanoparticles deposited on self-organized nano-ripple quartz substrates have been studied by... more Gold nanoparticles deposited on self-organized nano-ripple quartz substrates have been studied by spectroscopic Mueller matrix ellipsometry. The surface was found to have biaxial anisotropic optical properties. For electric field components normal to the ripples the periodic and disconnected nature of the in plane nanowires gives rise to an optical response dominated by the localized plasmon resonance. In the direction parallel to the ripples the gold nanoparticles are aligned closely leading to localized plasmon resonances in the infrared. As Au was deposited at an angle oblique to the surface normal, the gold nanoparticles were formed on the side of the ripples facing the incoming evaporation flux. This makes the gold particles slightly inclined, correspondingly the principal coordinate system of the biaxial dielectric tensor results tilted. The anisotropic plasmonic optical response results in a strong polarizing effect, making it suitable as a plasmonic nanowired grid polarizer.
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Papers by Marina Giordano