Self-similar properties of the far-infrared and optical absorption of fractal metallic clusters

Brouers, F.; Rauw, Dominique De; Clerc, Jean-Pierre; Giraud, G.

doi:10.1103/physrevb.49.14582

Cited by 18 publications

(11 citation statements)

References 7 publications

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“…The localization of optical eigenmodes, and associated strong field fluctuations can lead to a dramatic enhancement of many optical effects in fractals. [5][6][7] The theory of optical excitations in fractal clusters and percolation systems has been under development during the last decade, in particular, by Berry, 8 Stroud, 9 Bergman, 10 Fuchs and Claro, 11 Devaty, 12 Brouers, 13 Niklasson,14 and by Markel, Stockman, Shalaev and their co-workers. [5][6][7][15][16][17][18][19][20][21][22][23][24][25][26] Strong localization of dipolar eigenmodes in regions smaller than the wavelength was predicted in Ref.…”

Section: Introductionmentioning

confidence: 99%

Small-particle composites. I. Linear optical properties

et al. 1996

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Absorption and extinction spectra of fractal and nonfractal small-particle composites are studied. General solutions of the coupled-dipole equations with the exact operator for the dipole interaction ͑including the near-, intermediate-, and far-zone terms͒ are found and compared with those in the quasistatic approximation. Broadscale numerical simulations of optical spectra for clusters containing a large number of particles ͑up to 10 000͒ are performed. A significant fraction of dipolar eigenmodes in fractal aggregates is shown to be strongly localized. The eigenmodes cover a wide spectral region providing resonant enhancement in the visible and infrared parts of the spectrum. In contrast to previous predictions, the absorption spectrum is shown to be significantly different from the spectral distribution of the density of dipole eigenmodes. It clearly indicates the importance of symmetry properties of the modes and corresponding selection rules for the absorption by different modes in random fractal composites. Our experimental data obtained for extinction spectra of silver colloid fractal aggregates are in good agreement with the results of numerical simulations.

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Section: Introductionmentioning

confidence: 99%

Small-particle composites. I. Linear optical properties

et al. 1996

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“…Numerical simulation results are shown to be in excellent agreement with the experiment. In particular, our work is distinct from most previous works [5][6][7][8][9][10][11][12][13][14][15][16] in its focus on the interaction of fractal local resonances with Bragg scattering.…”

Section: Introductionmentioning

confidence: 82%

“…There is an extensive literature on optical properties of fractals formed from aggregation of metallic particles that are usually random in character. [5][6][7] There have been a similar abundance of studies on the electrical properties of fractal-shaped electrodes or self-similar circuits. [8][9][10] Electromagnetic functionalities of fractal patterns, such as Koch curves and Sierpinski gaskets, have been intensely investigated, e.g., for their applications as diffraction plates or radio antennas.…”

Section: Introductionmentioning

confidence: 99%

Three-dimensional metallic fractals and their photonic crystal characteristics

et al. 2008

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We report photonic properties of subwavelength three-dimensional ͑3D͒ metallic H-shaped fractals. The fractal structure supports localized resonances with relevant wavelength over ten times the sample size. Owing to the anisotropy inherent to the fractal geometry, the resonances and their induced band gaps are polarization dependent. The measured microwave transmission spectra agree well with simulations, and show the anisotropic response to be well described by an effective dielectric tensor. Using the three-dimensional H fractal as the basic unit, a microwave photonic crystal was fabricated, and its band-gap characteristics shown to display unique features of hybridization between local resonances and Bragg scattering. A photonic crystal of 3D fractals is an excellent microwave analog to an anisotropic electronic solid consisting of atoms or molecules with localized discrete energy levels.

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“…Such resonances would have to be present for the majority of our samples in order for triplets of depolarisation factors to sum up to unity. The peak structure of the SDF is reminiscent of the behaviour of fractal equivalent circuit models 44 of optical properties of percolating composites. Indeed acceptable fits to g(x) by this type of model are possible 26 , but a problem is that these models also have resonances at high x, which we do not observe in the SDF derived from experimental data.…”

Section: Spectral Density Functionsmentioning

confidence: 99%

Spectral density analysis of the optical properties of Ni-Al 2 O 3 nano-composite films

2011

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Thin films consisting of transition metal nanoparticles in an insulating oxide exhibit a high solar absorptance together with a low thermal emittance and are used as coatings on solar collector panels. In order to optimise the nanocomposites for this application a more detailed understanding of their optical properties is needed. Here we use a highly efficient recently developed numerical method to extract the spectral density function of nickel-aluminum oxide (Ni-Al 2 O 3 ) composites from experimental data on the dielectric permittivity in the visible and near-infrared wavelength ranges. Thin layers of Ni-Al 2 O 3 were produced by a sol-gel technique. Reflectance and transmittance spectra were measured by spectrophotometry in the wavelength range 300 to 2500 nm for films with thicknesses in the range 50 to 100 nm. Transmission electron microscopy showed crystalline Ni particles with sizes in the 3 to 10 nm range. The spectral density function shows a multi-peak structure with three or four peaks clearly visible. The peak positions are influenced by particle shape, local volume fraction distributions and particle-particle interactions giving rise to structural resonances in the response of the composite to an electromagnetic field.

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Self-similar properties of the far-infrared and optical absorption of fractal metallic clusters

Cited by 18 publications

References 7 publications

Small-particle composites. I. Linear optical properties

Small-particle composites. I. Linear optical properties

Three-dimensional metallic fractals and their photonic crystal characteristics

Spectral density analysis of the optical properties of Ni-Al 2 O 3 nano-composite films

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