Photo-Acoustic Spectroscopy Reveals Extrinsic Optical Chirality in GaAs-Based Nanowires Partially Covered with Gold

Petronijevic, Emilija; Leahu, Grigore; Belardini, A.; Centini, Marco; Voti, R. Li; Hakkarainen, Teemu; Koivusalo, Eero; Piton, Marcelo Rizzo; Suomalainen, Soile; Guina, Mircea; Sibilia, C.

doi:10.1007/s10765-018-2367-2

Cited by 19 publications

(13 citation statements)

References 35 publications

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“…This is rather expected for vertical high refractive index nanowires, where the absorption peak arises due to the mode, which is mainly defined by the radial boundary conditions of the nanowire core (as in dielectric waveguides). Therefore, the radius plays a major role in the spectral position of the absorption peak, while other geometric parameters have a minor influence, as we experimentally demonstrated in [17,18,30,31]. As expected, the shortest NW (L = 500 nm) has an enhanced C* only due to the first antinode of the resonant mode, while for L = 800 nm another antinode appears.…”

Section: Resultssupporting

confidence: 65%

Enhanced Near-Field Chirality in Periodic Arrays of Si Nanowires for Chiral Sensing

Petronijevic

Sibilia

2019

Molecules

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Nanomaterials can be specially designed to enhance optical chirality and their interaction with chiral molecules can lead to enhanced enantioselectivity. Here we propose periodic arrays of Si nanowires for the generation of enhanced near-field chirality. Such structures confine the incident electromagnetic field into specific resonant modes, which leads to an increase in local optical chirality. We investigate and optimize near-field chirality with respect to the geometric parameters and excitation scheme. Specially, we propose a simple experiment for the enhanced enantioselectivity, and optimize the average chirality depending on the possible position of the chiral molecule. We believe that such a simple achiral nanowire approach can be functionalized to give enhanced chirality in the spectral range of interest and thus lead to better discrimination of enantiomers.

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Section: Resultssupporting

confidence: 65%

Enhanced Near-Field Chirality in Periodic Arrays of Si Nanowires for Chiral Sensing

Petronijevic

Sibilia

2019

Molecules

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“…Plasmonics is promising for that matter as it can enhance interaction with electromagnetic fields at the nanoscale. Chirality can be designed [19] by breaking the symmetry in plasmonic nanomaterials during their fabrication, or with a proper oblique incidence set-up, as it was experimentally observed previously [20][21][22][23][24]. When a sample exhibits CD at normal incidence, it is said to be intrinsically chiral; on the contrary, in achiral samples the symmetry breaking can be induced by properly tilting the experimental set-up (extrinsic chirality).…”

Section: Introductionmentioning

confidence: 97%

Circular Dichroism in Low-Cost Plasmonics: 2D Arrays of Nanoholes in Silver

et al. 2020

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Arrays of nanoholes in metal are important plasmonic devices, proposed for applications spanning from biosensing to communications. In this work, we show that in such arrays the symmetry can be broken by means of the elliptical shape of the nanoholes, combined with the in-plane tilt of the ellipse axes away from the array symmetry lines. The array then differently interacts with circular polarizations of opposite handedness at normal incidence, i.e., it becomes intrinsically chiral. The measure of this difference is called circular dichroism (CD). The nanosphere lithography combined with tilted silver evaporation was employed as a low-cost fabrication technique. In this paper, we demonstrate intrinsic chirality and CD by measuring the extinction in the near-infrared range. We further employ numerical analysis to visualize the circular polarization coupling with the nanostructure. We find a good agreement between simulations and the experiment, meaning that the optimization can be used to further increase CD.

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“…Recently, we observed that GaAs nanowires (NWs) offered interesting waveguiding properties even for energies above the bandgap, thanks to the high refractive index of GaAs (in particular at 800 and 400 nm) [3]. We further verified, using photoacoustic spectroscopy, that when such GaAs NWs were partially covered in gold they exhibited strong extrinsic chirality due to the breaking of the symmetry induced by the asymmetric metal coating [11,12]. We also numerically investigated near-field chiral effects in high-refractive-index nanowires with [22] and without [23] an asymmetric plasmonic layer.…”

Section: Introductionmentioning

confidence: 81%

“…By breaking the symmetry of the nanostructure-light interaction, it is possible to observe a circular dichroism (CD) due to the so-called extrinsic chirality or pseudo chirality [6][7][8]. Chirality is the lack of mirror symmetry [9], and can be probed using photoacoustic techniques that are sensitive to the differential absorptions of opposite-handed light [10][11][12] or by techniques sensitive to symmetry breaking such as second harmonic generation-circular dichroism (SHG-CD) [13,14]. In the case of extrinsic chirality, the high sensitivity of SHG is related to the fact that SHG can only occur in systems with broken inversion symmetry, enabling background-free measurements and leading to higher CD responses with respect other measurement systems [15].…”

Section: Introductionmentioning

confidence: 99%

Circular Dichroism in the Second Harmonic Field Evidenced by Asymmetric Au Coated GaAs Nanowires

et al. 2020

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Optical circular dichroism (CD) is an important phenomenon in nanophotonics, that addresses top level applications such as circular polarized photon generation in optics, enantiomeric recognition in biophotonics and so on. Chiral nanostructures can lead to high CD, but the fabrication process usually requires a large effort, and extrinsic chiral samples can be produced by simpler techniques. Glancing angle deposition of gold on GaAs nanowires can (NWs) induces a symmetry breaking that leads to an optical CD response that mimics chiral behavior. The GaAs NWs have been fabricated by a self-catalyzed, bottom-up approach, leading to large surfaces and high-quality samples at a relatively low cost. Here, we investigate the second harmonic generation circular dichroism (SHG-CD) signal on GaAs nanowires partially covered with Au. SHG is a nonlinear process of even order, and thus extremely sensitive to symmetry breaking. Therefore, the visibility of the signal is very high when the fabricated samples present resonances at first and second harmonic frequencies (i.e., 800 and 400 nm, in our case).

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Photo-Acoustic Spectroscopy Reveals Extrinsic Optical Chirality in GaAs-Based Nanowires Partially Covered with Gold

Cited by 19 publications

References 35 publications

Enhanced Near-Field Chirality in Periodic Arrays of Si Nanowires for Chiral Sensing

Enhanced Near-Field Chirality in Periodic Arrays of Si Nanowires for Chiral Sensing

Circular Dichroism in Low-Cost Plasmonics: 2D Arrays of Nanoholes in Silver

Circular Dichroism in the Second Harmonic Field Evidenced by Asymmetric Au Coated GaAs Nanowires

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