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| 2. |
- Svedendahl, Mikael, et al.
(författare)
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Refractometric sensing using propagating versus localized surface plasmons : a direct comparison
- 2009
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Ingår i: Nano letters (Print). - : American Chemical Society (ACS). - 1530-6984 .- 1530-6992. ; 9:12, s. 4428-4433
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Tidskriftsartikel (refereegranskat)abstract
- We present a direct experimental comparison between the refractive index sensing capabilities of localized surface plasmon resonances (LSPRs) in gold nanodisks and propagating surface plasmon resonances (SPRs) on 50 nm gold films. The comparison is made using identical experimental conditions, and for the same resonance wavelength, lambda(SP) congruent with 700 nm. Biosensing experiments with biotin-avidin coupling reveal that the two sensing platforms have very similar performance, despite a superior bulk refractive index sensing figure of merit for the SPR sensor. The results demonstrate that LSPR sensing based on simple transmission or reflection measurements is a highly competitive technique compared to the traditional SPR sensor.
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| 3. |
- Alaverdyan, Yury, 1976, et al.
(författare)
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Optical antennas based on coupled nanoholes in thin metal films
- 2007
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Ingår i: Nature Physics. - : Springer Science and Business Media LLC. - 1745-2481 .- 1745-2473. ; 3:12, s. 884-889
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Tidskriftsartikel (refereegranskat)abstract
- The ability to control optical effects at the nanoscale is a challenge that could be of great importance for a range of photonic applications. However, progress requires a deep understanding of the relationship between near-field and far-field properties of the individual elements of the nanostructure, as well as of the role of nano-optical interactions. Here, we show that the strong interaction between nanoholes in optically thin metal films can be used to readily tune their spectral response and visibility. Control of this interaction in short chains of nanoholes enables either amplification or almost total suppression of the scattered light. The phenomena are interpreted in terms of hole coupling mediated via antisymmetric surface plasmon polaritons, which makes the nanohole chains effectively behave as linear wire antennas.
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| 5. |
- Alegret, Joan, 1977, et al.
(författare)
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Green's tensor calculations of plasmon resonances of single holes and hole pairs in thin gold films
- 2008
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Ingår i: New Journal of Physics. - Bristol, UK : IOP Publishing. - 1367-2630. ; 10, s. 13-
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Tidskriftsartikel (refereegranskat)abstract
- We present numerical calculations of the plasmon properties of single-hole and hole-pair structures in optically thin gold films obtained with the Green's tensor formalism for stratified media. The method can be used to obtain the optical properties of a given hole system, without problems associated with the truncation of the infinite metal film. The calculations are compared with previously published experimental data and an excellent agreement is found. In particular, the calculations are shown to reproduce the evolution of the hole plasmon resonance spectrum as a function of hole diameter, film thickness and hole separation.
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| 6. |
- Alegret, Joan, 1977, et al.
(författare)
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Plasmonic properties of silver trimers with trigonal symmetry fabricated by electron-beam lithography
- 2008
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Ingår i: Journal of Physical Chemistry C. - : American Chemical Society (ACS). - 1932-7447 .- 1932-7455. ; 112:37, s. 14313-14317
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Tidskriftsartikel (refereegranskat)abstract
- We investigate the dipolar plasmon modes of nanoparticle trimers formed by three equal silver disks of diameter D = 100 nm located on the vertexes of an equilateral triangle. Samples were fabricated by electron-beam lithography and studied experimentally by dark-field spectroscopy. The results are found to be in good agreement with electrodynamical simulations based on the discrete dipole approximation (DDA). Similar to nanoparticle dimers, the trimer system exhibits two hybridized dipole resonances to the red and to the blue of the single particle resonance. However, the far-field spectra are polarization-insensitive for light incident normal to the plane of the trimer, and the peak shifts, which occur as the edge-to-edge distance d between the particles decrease, are smaller than for dimers. Moreover, we find that the dipolar displacement patterns are well described by linear combinations of bonding and antibonding symmetry adapted coordinates obtained through symmetry analysis based on the ideal D-3h point-group.
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| 9. |
- Andreasson, Jakob, 1975, et al.
(författare)
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Electron-lattice interactions in the perovskite LaFe0.5Cr0.5O3 characterized by optical spectroscopy and LDA plus U calculations
- 2009
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Ingår i: Physical Review B. Condensed Matter and Materials Physics. - 1098-0121 .- 1550-235X .- 2469-9950 .- 2469-9969. ; 80:7, s. 075103-
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Tidskriftsartikel (refereegranskat)abstract
- We use resonance Raman scattering (incident photon energies between 1.8 and 4.13 eV), LDA+U calculations, spectroscopic ellipsometry, and oblique IR reflectivity to characterize the strong electron-phonon interactions in the disordered perovskite LaFe0.5Cr0.5O3. When the photon energy coincides with a Cr to Fe Mott-Hubbard transfer gap around 2.4 eV the electron-phonon interaction is manifested by a Franck-Condon effect with exceptional first-and higher order scattering of a local oxygen breathing mode. At higher incident energies we observe a superposition of Franck-Condon scattering and Frohlich interaction induced infrared active longitudinal optical two-phonon scattering activated mainly by O to Fe charge transfer. Our results establish LaFe0.5Cr0.5O3 as a model compound for research on electron-phonon interactions in strongly correlated complex systems and show that Franck-Condon scattering in complex solids is not limited to Jahn-Teller active compounds.
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| 10. |
- Andreasson, Jakob, 1975, et al.
(författare)
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Electron-phonon interactions in perovskites containing Fe and Cr studied by Raman scattering using oxygen-isotope and cation substitution
- 2008
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Ingår i: Physical Review B. Condensed Matter and Materials Physics. - 1098-0121 .- 1550-235X .- 2469-9950 .- 2469-9969. ; 78:23, s. 235103-
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Tidskriftsartikel (refereegranskat)abstract
- We use temperature-dependent inelastic light scattering to study the origin of the strong multiphonon scattering of a local oxygen breathing mode present in the mixed B-site orthorhombic (space group Pnma) perovskite LaFe0.5Cr0.5O3 but absent in isostructural LaFeO3 and LaCrO3. It is seen that the multiphonon scattering is critically sensitive to the presence of both Fe and Cr ions on the B site. These results support our interpretation that the multiphonon scattering is activated by local electron-phonon interactions according to the Franck-Condon picture following an Fe-Cr charge transfer. Further, O-18 substitution is performed on the x=0, 0.04, and 0.5 compounds and clearly shows that all modes appearing above the first-order phonon-scattering region in these compounds originate from higher-order oxygen stretching vibrations. In particular this is the case for the strong second-order scattering dominating the scattering response in LaFeO3. Accordingly we propose that these modes are generated by infrared-active longitudinal optical (IR LO) two-phonon and combination scattering activated by Frohlich interaction. For x=0.02 and 0.04 the characteristic IR LO two-phonon and Franck-Condon multiphonon-scattering profiles mix. We also study the influence of isovalent cation substitution and Sr doping in AFe(0.5)Cr(0.5)O(3) (A=La, Nd, and Gd) and La1-ySryFe0.5Cr0.5O3-delta (y=0, 0.16, and 0.5) on the strong electron-phonon coupling present in LaFe0.5Cr0.5O3. The Franck-Condon effect in LaFe0.5Cr0.5O3, is not significantly affected by isovalent A-site substitution, despite the increasing orthorhombic distortion associated with decreasing A-site ionic radii. On the contrary, aliovalent Sr doping causes a rapid decrease in the Franck-Condon scattering. This shows that the strong electron-phonon coupling in these compounds is highly sensitive to local lattice and electronic decoherence but insensitive to global lattice distortions. Finally, a preliminary assignment of the A(g) and B-2g phonon modes in AFe(0.5)Cr(0.5)O(3) (A=La, Nd, and Gd) is made based on the present observations and published results for LaCrO3 and AMnO(3). The modes associated with oxygen octahedral tilt and bending vibrations are heavily influenced by the magnitude of the orthorhombic distortion.
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