Nano-plasmonic chiral S.H.G. emitters
| Autor: | Radoslaw Kolkowski, Lucia Petti, Clement Lafargue, Joseph Zyss |
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| Jazyk: | angličtina |
| Rok vydání: | 2015 |
| Předmět: | |
| Zdroj: | Conference on Lasers and Electro-Optics & European Quantum Electronics Conference (CLEO Europe 2015), Germany, Munich, 21-25 June 2015 info:cnr-pdr/source/autori:Radoslaw Kolkowski, Lucia Petti, Clement Lafargue, and Joseph Zyss/congresso_nome:Conference on Lasers and Electro-Optics & European Quantum Electronics Conference (CLEO Europe 2015)/congresso_luogo:Germany, Munich/congresso_data:21-25 June 2015/anno:2015/pagina_da:/pagina_a:/intervallo_pagine |
| Popis: | New chiroptical experimental schemes allowing for the local control of the polarization states of light are being actively searched [1]. Nanoplasmonic structures and meta-materials are appealing candidates towards on-demand field engineering that could have an impact on biochemistry towards e.g. biosensors with enantiomer selectivity, nanoscale chiral recognition and (bio-)material sciences. We report here on 2-D non-centrosymetric chiral gold nanostructures, that exhibit a giant chiroptical second harmonic response (C-SHG). Such structures could find interesting application in watermarking, as this early demonstration suggests. SHG is a benchmarking symmetry sensitive quadratic nonlinear optical effect that may sustain strong resonant enhancement, via plasmon modes i.e. collective oscillations of free electrons and photon at metal-dielectric interfaces, hybridized to the electromagnetic field. In the case of nano-plasmonics, the shape and dimensions of tailored nanostructures determines both the resonant modes and eventual hot spots, at the origin, of possible SHG enhancement, depending on their local symmetry. We will report on nano-assemblies of non-centrosymmetric triangular gold nanoparticles, following a design based on a combination of tensor symmetry and chirality considerations. Obtained by e-beam lithography, the size of the particles is less than 150 nm and they are arranged in quadruplets with respectively left- or right-handed chirality (see fig. 1), at close enough positions that allow for localized plasmon mode coupling, thus forming a plasmonic molecule [2], with pattern parameters smaller than the excitation wavelength. As a result, the details of the structure are beyond the resolution of classical linear optical microscopy which does not permit to evidence the chiral nature and handedness of such a plasmonic molecule . However, high circular dichroism can be observed in the experimental frame of a polarization-resolved two-photon microscope injected by a pulsed Ti:Sa laser at the resonant frequency of 850nm. Indeed, the SHG level for a right-handed circularly polarized beam impinging on a "right" plasmonic enantiomer was measured to be significantly higher compared to that from the "left" enantiomer or to the case of left-handed circularly polarized impinging fundamental beam (see fig.1 right), in agreement with our numerical simulations. We propose to use these structures towards a novel watermarking strategy as they are invisible under classical linear microscopy, but require a nonlinear read-out scheme which we have successfully demonstrated by means of a "right-left" encoded image in a nanoplasmonic array. Finally we will discuss the benefits and prospects of our approach in term of near-field engineering. |
| Databáze: | OpenAIRE |
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