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Träfflista för sökning "L773:1094 4087 ;pers:(Käll Mikael 1963)"

Sökning: L773:1094 4087 > Käll Mikael 1963

  • Resultat 1-10 av 14
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1.
  • Antosiewicz, Tomasz, 1981, et al. (författare)
  • A simple model for the resonance shift of localized plasmons due to dielectric particle adhesion
  • 2012
  • Ingår i: Optics Express. - 1094-4087 .- 1094-4087. ; 20:1, s. 524-533
  • Tidskriftsartikel (refereegranskat)abstract
    • Ultrasensitive detectors based on localized surface plasmonresonance refractive index sensing are capable of detecting very lownumbers of molecules for biochemical analysis. It is well known that thesensitivity of such sensors crucially depend on the spatial distribution ofthe electromagnetic field around the metal surface. However, the preciseconnection between local field enhancement and resonance shift is seldomdiscussed. Using the quasistatic approximation, we developed a model thatrelates the sensitivity of a nanoplasmonic resonator to the local field inwhich the analyte is placed. The model, corroborated by finite-differencetime-domain simulations, may be used to estimate the magnitude of theshift as a function of the properties of the sensed object – permittivity andvolume – and its location on the surface of the resonator. It requires onlya computation of the resonant field induced by the metal structure and istherefore suitable for numerical optimization of nanoplasmonic sensors.
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2.
  • Brian, Björn, 1980, et al. (författare)
  • Sensitivity enhancement of nanoplasmonic sensors on low refractive index substrates
  • 2009
  • Ingår i: Optics Express. - 1094-4087 .- 1094-4087. ; 17:3, s. 2015-2023
  • Tidskriftsartikel (refereegranskat)abstract
    • Metal films perforated by nanoholes constitute a powerful platform for surface plasmon resonance biosensing. We find that the refractive index sensitivity of nanohole arrays increases if their resonance is red-shifted by increasing the separation distance between holes. However, an additional sensitivity enhancement occurs if the nanohole sensors are manufactured on low index substrates, despite the fact such substrates significantly blue-shift the resonance. We find a ∼40% higher bulk refractive index sensitivity for a system of -100 nm holes in 20 nm gold films fabricated on Teflon substrates (n=1.32) compared to the case when conventional glass substrates (n=1.52) are used. A similar improvement is observed for the case when a thin layer of dielectric material is deposited on the samples. These results can be understood by considering the electric field distribution induced by the so-called antisymmetric surface plasmon polariton in the thin gold films.
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3.
  • Garcia-Etxarri, Aitzol, et al. (författare)
  • A combination of concave/convex surfaces for field-enhancement optimization: the indented nanocone
  • 2012
  • Ingår i: Optics Express. - 1094-4087 .- 1094-4087. ; 20:23, s. 25201-25212
  • Tidskriftsartikel (refereegranskat)abstract
    • We introduce a design strategy to maximize the Near Field (NF)enhancement on plasmonic antennas. We start by identifying and studyingthe basic electromagnetic effects that contribute to the electric near fieldenhancement. On a second step, we show how the concatenation of a convexand a concave surface allows merging all the effects on a single, continuousnanoantenna. As an example of this NF maximization strategy, we engineera nanostructure, the indented nanocone. This structure, combines all thestudied NF maximization effects with a synergistic boost provided bya Fano-like interference effect activated by the presence of the concavesurface. As a result, the antenna exhibits a NF amplitude enhancement of 800, which transforms into 1600 when coupled to a perfect metallicsurface. This strong enhancement makes the proposed structure a robustcandidate to be used in field enhancement based technologies. Furtherelaborations of the concept may produce even larger and more effectiveenhancements.
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4.
  • Hartling, T., et al. (författare)
  • Optically controlled interparticle distance tuning and welding of single gold nanoparticle pairs by photochemical metal deposition
  • 2008
  • Ingår i: Optics Express. - 1094-4087 .- 1094-4087. ; 16:16, s. 12362-12371
  • Tidskriftsartikel (refereegranskat)abstract
    • We report on the in-situ controlled tuning of the particle gap in single pairs of gold nanodisks by photochemical metal deposition. The optically induced growth of nanodisk dimers fabricated by electron beam lithography leads to a decrease of the interparticle gap width down to 0 nm. Due to the increasing particle size and stronger plasmonic coupling, a smooth redshift of the localized surface plasmon (LSP) resonances is observed in such particle pairs during the growth process. The interparticle gap width, and hence the LSP resonance, can be tuned to any desired spectral position. The experimental results we obtain with this nanoscale fabrication technique are well described by the so-called plasmon ruler equation. Consequently, both the changes in particle diameter as well as in gap width can be characterized in-situ via far-field read-out of the optical properties of the dimers.
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5.
  • Kvarnström, Mats, 1974, et al. (författare)
  • Image analysis algorithms for cell contour recognition in budding yeast
  • 2008
  • Ingår i: Optics Express. - 1094-4087 .- 1094-4087. ; 16:17, s. 12943-12957
  • Tidskriftsartikel (refereegranskat)abstract
    • Quantification of protein abundance and subcellular localization dynamics from fluorescence microscopy images is of high contemporary interest in cell and molecular biology. For large-scale studies of cell populations and for time-lapse studies, such quantitative analysiscan not be performed effectively without some kind of automated image analysis tool. Here, we present fast algorithms for automatic cell contour recognition in bright field images, optimized to the model organismbudding yeast (Saccharomyces cerevisiae). The cell contours can be used to effectively quantify cell morphology parameters as well as protein abundance and subcellular localization from overlaid fluorescence data.
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6.
  • Lehmuskero, Anni, 1982, et al. (författare)
  • Plasmonic particles set into fast orbital motion by an optical vortex beam WARI SC, 1992, JOURNAL OF MODERN OPTICS, V39, P1097
  • 2014
  • Ingår i: Optics Express. - : The Optical Society. - 1094-4087 .- 1094-4087. ; 22:4, s. 4349-4356
  • Tidskriftsartikel (refereegranskat)abstract
    • We optically trap plasmonic gold particles in two dimensions and set them into circular motion around the optical axis using a helically phased vortex laser beam. The orbiting frequency of the particles reaches 86 Hz, which corresponds to a particle velocity of the order 1 mm per second, for an incident laser power of a few tens of milliwatts. The experimentally determined orbiting frequencies are found to be well in line with the notion that the beam carries an orbital angular momentum of hl per photon. (C) 2014 Optical Society of America
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7.
  • Martinez Llinas, Jade, 1985, et al. (författare)
  • A Gaussian reflective metasurface for advanced wavefront manipulation
  • 2019
  • Ingår i: Optics Express. - 1094-4087 .- 1094-4087. ; 27:15, s. 21069-21082
  • Tidskriftsartikel (refereegranskat)abstract
    • Metasurfaces enable us to control the fundamental properties of light with unprecedented flexibility. However, most metasurfaces realized to date aim at modifying plane waves. While the manipulation of nonplanar wavefronts is encountered in a diverse number of applications, their control using metasurfaces is still in its infancy. Here we design a metareflector able to reflect a diverging Gaussian beam back onto itself with efficiency over 90% and focusing at an arbitrary distance. We outline a clear route towards the design of complex metareflectors that can find applications as diverse as optical tweezing, lasing, and quantum optics.
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8.
  • Mendoza-Galvan, A., et al. (författare)
  • Fano interference in supported gold nanosandwiches with weakly coupled nanodisks
  • 2012
  • Ingår i: Optics Express. - 1094-4087 .- 1094-4087. ; 20:28, s. 29646-29658
  • Tidskriftsartikel (refereegranskat)abstract
    • We studied the far-field optical response of supported gold-silica-gold nanosandwiches using spectroscopic ellipsometry, reflectance and transmittance measurements. Although transmittance data clearly shows that the gold nanodisks in the sandwich structure interact very weakly, oblique reflectance spectra of s- and p-polarized light show clearly asymmetric line-shapes of the Fano type. However, all experimental results are very well described by modeling the gold nanodisks as oblate spheroids and by employing a 2 x 2 scattering matrix formulation of the Fresnel coefficients provided by an island film theory. In particular, the Fano asymmetry can be explained in terms of interference between the scattered waves from the decoupled nanodisks in the spectral range limited by their respective plasmon resonances. We also show that the reflectance and ellipsometry spectra can be described by a three-layer system with uniaxial effective dielectric functions.
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9.
  • Mendoza-Galvan, A., et al. (författare)
  • Optical response of supported gold nanodisks
  • 2011
  • Ingår i: Optics Express. - : Optical Society of America (OSA). - 1094-4087. ; 19:13, s. 12093-12107
  • Tidskriftsartikel (refereegranskat)abstract
    • It is shown that the ellipsometric spectra of short range ordered planar arrays of gold nanodisks supported on glass substrates can be described by modeling the nanostructured arrays as uniaxial homogeneous layers with dielectric functions of the Lorentz type. However, appreciable deviations from experimental data are observed in calculated spectra of irradiance measurements. A qualitative and quantitative description of all measured spectra is obtained with a uniaxial effective medium dielectric function in which the nanodisks are modeled as oblate spheroids. Dynamic depolarization factors in the long-wavelength approximation and interaction with the substrate are considered. Similar results are obtained calculating the optical spectra using the island-film theory. Nevertheless, a small in-plane anisotropy and quadrupolar coupling effects reveal a very complex optical response of the nanostructured arrays.
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10.
  • Miljkovic, Vladimir, 1982, et al. (författare)
  • Mode-specific directional emission from hybridized particle-on-a-film plasmons
  • 2011
  • Ingår i: Optics Express. - 1094-4087. ; 19:14, s. 12856-12864
  • Tidskriftsartikel (refereegranskat)abstract
    • We investigate the electromagnetic interaction between a gold nanoparticle and a thin gold film on a glass substrate. The coupling between the particle plasmons and the surface plasmon polaritons of the film leads to the formation of two localized hybrid modes, one low-energy. film-like. plasmon and one high-energy plasmon dominated by the nanoparticle. We find that the two modes have completely different directional scattering patterns on the glass side of the film. The high-energy mode displays a characteristic dipole emission pattern while the low-energy mode sends out a substantial part of its radiation in directions parallel to the particle dipole moment. The relative strength of the two radiation patterns vary strongly with the distance between the particle and the film, as determined by the degree of particle-film hybridization. (C) 2011 Optical Society of America
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  • Resultat 1-10 av 14

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