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See detailChirality in nonlinear-optical response of planar G-shaped nanostructures
Mamonov, E.A.; Murzina, T.V.; Kolmychek, I.A. et al

in Optics Express (2012), 20(8), 8518

Chirality effects in optical second harmonic generation (SHG) are studied in periodic planar arrays of gold G-shaped nanostructures. We show that G-shaped structures of different handedness demonstrate ... [more ▼]

Chirality effects in optical second harmonic generation (SHG) are studied in periodic planar arrays of gold G-shaped nanostructures. We show that G-shaped structures of different handedness demonstrate different SHG efficiency for the left and right circular polarizations, as well as the opposite directions of the SHG polarization plane rotation. The observed effects are interpreted as the appearance of chirality in the SHG response which allows clear distinguishing of two enantiomers. [less ▲]

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See detailPlasmon-Enhanced Sub-Wavelength Laser Ablation: Plasmonic Nanojets
Valev, V.K.; Denkova, D.; Zheng, X. et al

in Advanced Materials (2012), 24

Plasmonic hotspots are regions on the surface of metal nanostructures where light causes very strong oscillation of the electrons. Because electron oscillations constitute an electric current and because ... [more ▼]

Plasmonic hotspots are regions on the surface of metal nanostructures where light causes very strong oscillation of the electrons. Because electron oscillations constitute an electric current and because electric currents heat up the material the same way an electric stove heats up in the kitchen, the plasmonic hotspots are extremely hot. So hot that they can melt the gold in a spot much smaller than the wavelength of light. We were successfully able to demonstrate that this tiny little pool of molten gold can give rise to the smallest nanojets ever observed. [less ▲]

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See detailDistributing the Optical Near-Field for Efficient Field-Enhancements in Nanostructures
Valev, V; De Clercq, B; Biris, C et al

in Advanced Materials (2012), 24

Circularly polarized light imparts a sense of rotation on the electron density in ring-shaped gold nanostructures. As a consequence, the near-field enhancement becomes homogeneous on the surface of the ... [more ▼]

Circularly polarized light imparts a sense of rotation on the electron density in ring-shaped gold nanostructures. As a consequence, the near-field enhancement becomes homogeneous on the surface of the nanostructures, thereby increasing the opportunity for interaction with molecules. This type of nanostructured samples can find a broad range of applications in chemical processes where the interaction between molecules and local field enhancements play an important role. [less ▲]

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See detailRobustness of the scanning second harmonic generation microscopy technique for characterization of hotspot patterns in plasmonic nanomaterials
Valev, VK; De Clercq, B; Zheng, X et al

in Proceedings of SPIE (2012), 8424

Scanning second harmonic generation (SHG) microscopy is becoming an important tool for characterizing nanopatterned metal surfaces and mapping plasmonic local field enhancements. Here we study G-shaped ... [more ▼]

Scanning second harmonic generation (SHG) microscopy is becoming an important tool for characterizing nanopatterned metal surfaces and mapping plasmonic local field enhancements. Here we study G-shaped and mirror-G-shaped gold nanostructures and test the robustness of the experimental results versus the direction of scanning, the numerical aperture of the objective, the magnification, and the size of the laser spot on the sample. We find that none of these parameters has a significant influence on the experimental results. [less ▲]

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See detailSecond harmonic hotspots at the edges of the unit cells in G-shaped gold nanostructures
Valev, VK; Osley, EJ; De Clercq, B et al

in Proceedings of SPIE (2012), 8424

We report our latest results on second harmonic generation (SHG) microscopy from arrays of G-shaped chiral gold nanostructures. The nanostructures are arranged in unit cells composed of four Gs, each ... [more ▼]

We report our latest results on second harmonic generation (SHG) microscopy from arrays of G-shaped chiral gold nanostructures. The nanostructures are arranged in unit cells composed of four Gs, each rotated at 90° with respect to its neighbors. As it has already been demonstrated, for linearly polarized light, these unit cells yield a pattern of four SHG hotspots. However, upon increasing the pitch of the nanostructured arrays, extra hotspots can be observed at the edges of the unit cells. While the origin of these extra hotspots remains to be elucidated, their position indicates a relationship to coupling behavior between the unit cells. [less ▲]

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See detailThe role of chiral local field enhancements below the resolution limit of Second Harmonic Generation microscopy
Valev, V.; Clercq, B.; Zheng, X. et al

in Optics Express (2011), 20(1), 256

While it has been demonstrated that, above its resolution limit, Second Harmonic Generation (SHG) microscopy can map chiral local field enhancements, below that limit, structural defects were found to ... [more ▼]

While it has been demonstrated that, above its resolution limit, Second Harmonic Generation (SHG) microscopy can map chiral local field enhancements, below that limit, structural defects were found to play a major role. Here we show that, even below the resolution limit, the contributions from chiral local field enhancements to the SHG signal can dominate over those by structural defects. We report highly homogeneous SHG micrographs of star-shaped gold nanostructures, where the SHG circular dichroism effect is clearly visible from virtually every single nanostructure. Most likely, size and geometry determine the dominant contributions to the SHG signal in nanostructured systems. [less ▲]

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See detailHotspot Decorations Map Plasmonic Patterns with the Resolution of Scanning Probe Techniques
Valev, V. K.; Silhanek, Alejandro ULg; Jeyaram, Y. et al

in Physical Review Letters (2011), 106(22),

In high definition mapping of the plasmonic patterns on the surfaces of nanostructures, the diffraction limit of light remains an important obstacle. Here we demonstrate that this diffraction limit can be ... [more ▼]

In high definition mapping of the plasmonic patterns on the surfaces of nanostructures, the diffraction limit of light remains an important obstacle. Here we demonstrate that this diffraction limit can be completely circumvented. We show that upon illuminating nanostructures made of nickel and palladium, the resulting surface-plasmon pattern is imprinted on the structures themselves; the hotspots (regions of local field enhancement) are decorated with overgrowths, allowing for their subsequent imaging with scanning-probe techniques. The resulting resolution of plasmon pattern imaging is correspondingly improved. [less ▲]

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See detailCoherent and incoherent second harmonic generation in planar G-shaped nanostructures
Mamonov, E. A.; Murzina, T. V.; Kolmychek, I. A. et al

in Optics Letters (2011), 36(18), 3681-3683

Azimuthal anisotropy of Stokes parameters of the second harmonic generation ( SHG) generated and observed in reflection from a periodic planar area of G-shaped gold nanostructures is studied. A strong ... [more ▼]

Azimuthal anisotropy of Stokes parameters of the second harmonic generation ( SHG) generated and observed in reflection from a periodic planar area of G-shaped gold nanostructures is studied. A strong anisotropy of both coherent and incoherent SHG components is observed. Finite-difference time-domain calculations prove that the observed effects are due to the anisotropic enhancement of the fundamental radiation within the G-shaped structures. (C) 2011 Optical Society of America [less ▲]

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See detailLinearly polarized second harmonic generation microscopy reveals chirality (vol 18, pg 8286, 2010)
Valev, V. K.; Silhanek, Alejandro ULg; Smisdom, N. et al

in Optics Express (2011), 19(10), 9242-9244

An erratum is presented to clarify both the direction of light polarization in our experiments and the unit cell geometry of the samples. Additionally, the spectral dependence of the second harmonic ... [more ▼]

An erratum is presented to clarify both the direction of light polarization in our experiments and the unit cell geometry of the samples. Additionally, the spectral dependence of the second harmonic generation response in the G-shaped nanostructures made of gold is corrected. These changes do not affect our previous conclusions. (C) 2011 Optical Society of America [less ▲]

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See detailAsymmetric Optical Second-Harmonic Generation from Chiral G-Shaped Gold Nanostructures
Valev, V. K.; Silhanek, Alejandro ULg; Verellen, N. et al

in Physical Review Letters (2010), 104(12),

We present a new electromagnetic phenomenon-the asymmetric second-harmonic generation from planar chiral structures. The effect consists in distinguishing the handedness of a chiral material by rotating ... [more ▼]

We present a new electromagnetic phenomenon-the asymmetric second-harmonic generation from planar chiral structures. The effect consists in distinguishing the handedness of a chiral material by rotating the sample in an experiment involving solely linearly polarized light. This phenomenon originates in the surface plasmon resonance of chiral gold nanostructures, where homodyne interference of anisotropic and chiral electric and/or magnetic multipoles appears to play an important role. [less ▲]

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See detailLinearly polarized second harmonic generation microscopy reveals chirality
Valev, V. K.; Silhanek, Alejandro ULg; Smisdom, N. et al

in Optics Express (2010), 18(8), 8286-8293

In optics, chirality is typically associated with circularly polarized light. Here we present a novel way to detect the handedness of chiral materials with linearly polarized light. We performed Second ... [more ▼]

In optics, chirality is typically associated with circularly polarized light. Here we present a novel way to detect the handedness of chiral materials with linearly polarized light. We performed Second Harmonic Generation (SHG) microscopy on G-shaped planar chiral nanostructures made of gold. The SHG response originates in distinctive hotspots, whose arrangement is dependent of the handedness. These results uncover new directions for studying chirality in artificial materials. (C) 2010 Optical Society of America [less ▲]

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See detailA Study of Chirality in Gold Nanostructures with Second Harmonic Generation
Valev, V. K.; Silhanek, Alejandro ULg; Gillijns, W. et al

in Acta Physica Polonica A (2009), 116(4), 498-500

We present the second harmonic generation - circular dichroism response from C-shaped gold nanostructures for P-polarized incoming light. By eliminating the contributions of anisotropy to the signal, an ... [more ▼]

We present the second harmonic generation - circular dichroism response from C-shaped gold nanostructures for P-polarized incoming light. By eliminating the contributions of anisotropy to the signal, an absolute measure of the second harmonic generation - circular dichroism is presented. The system of planar nanostructures is an excellent model for studying the correlation between optical properties and chiral morphology at the nanoscale. Samples with both enantiomorphs of the chiral pattern were prepared and, demonstrating the unambiguous presence of chirality, the second harmonic generation - circular dichroism response from two such samples was fitted simultaneously with a single set of fitting parameters. [less ▲]

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See detailPlasmonic Ratchet Wheels: Switching Circular Dichroism by Arranging Chiral Nanostructures
Valev, V. K.; Smisdom, N.; Silhanek, Alejandro ULg et al

in Nano Letters (2009), 9(11), 3945-3948

We demonstrate circular dichroism (CD) in the second harmonic generation (SHG) signal from chiral assemblies of G-shaped nanostructures made of gold. The arrangement of the G shapes is crucial since upon ... [more ▼]

We demonstrate circular dichroism (CD) in the second harmonic generation (SHG) signal from chiral assemblies of G-shaped nanostructures made of gold. The arrangement of the G shapes is crucial since upon reordering them the SHG-CD effect disappears. Microscopy reveals SHG "hotspots" assemblies, which originate in enantiomerically sensitive plasmon modes, having the novel property of exhibiting a chiral geometry themselves in relation with the handedness of the material. These results open new frontiers in studying chirality. [less ▲]

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