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Register a new userThermal emission from three-dimensional arrays of gold nanoparticles
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Vassilios Yannopapas
Publication date
2006
fields
Physics
and research's language is
English
Authors
Vassilios Yannopapas
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We study the blackbody spectrum from slabs of three-dimensional metallodielectric photonic crystals consisting of gold nanoparticles using an ab initio multiple-scattering method. The spectra are calculated for different photonic-crystal slab thicknesses, particle radii and hosting materials. We find in particular that such crystals exhibit a broadband emission spectrum above a specific cutoff frequency with emissivity of about 90%. The studied photonic crystals can be used as efficient selective emitters and can therefore find application in thermophotovoltaics and sensing.
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The spectral characteristics of near-field thermal emission from nanoparticle arrays are explained by comparison to the dispersions for propagating modes. Using the coupled dipole model, we analytically calculate the spectral emission from single particles, chains, planes, and 3D arrays of SiO2 and SiC. We show that the differences in their spectra are due to the existence or absence of propagating surface phonon polariton modes and that the emission is dominated by these modes when they are present. This work paves the way for understanding and control of near-field radiation in nanofluids, nanoparticle beds, and certain metamaterials.
We consider the three dimensional array $mathcal{A} = {a_{i,j,k}}_{1le i,j,k le n}$, with $a_{i,j,k} in [0,1]$, and the two random statistics $T_{1}:= sum_{i=1}^n sum_{j=1}^n a_{i,j,sigma(i)}$ and $T_{2}:= sum_{i=1}^{n} a_{i,sigma(i),pi(i)}$, where $sigma$ and $pi$ are chosen independently from the set of permutations of ${1,2,ldots,n }.$ These can be viewed as natural three dimensional generalizations of the statistic $T_{3}=sum_{i=1}^{n} a_{i,sigma(i)}$, considered by Hoeffding cite{Hoe51}. Here we give Bernstein type concentration inequalities for $T_{1}$ and $T_{2}$ by extending the argument for concentration of $T_{3}$ by Chatterjee cite{Cha05}.
We report the investigation of the generation and detection of GHz coherent acoustic phonons in plasmonic gold nanoparticles superlattices (NPS). The experiments have been performed from an optical femtosecond pump-probe scheme across the optical plasmon resonance of the superlattice. Our experiments allow to estimate the collective elastic response (sound velocity) of the NPS as well as an estimate of the nano-contact elastic stiffness. It appears that the light-induced coherent acoustic phonon pulse has a typical in-depth spatial extension of about 45 nm which is roughly 4 times the optical skin depth in gold. The modeling of the transient optical reflectivity indicates that the mechanism of phonon generation is achieved through ultrafast heating of the NPS assisted by light excitation of the volume plasmon. These results demonstrate how it is possible to map the photon-electron-phonon interaction in subwavelength nanostructures.
We measured the far-field emission patterns in three dimensions of flat organic dye microlasers using a solid angle scanner. Polymer-based microcavities of ribbon shape (i.e., Fabry-Perot type) were investigated. Out of plane emission from the cavities was observed, with significant differences for the two cases of resonators either fully supported by the substrate or sustained by a pedestal. In both cases, the emission diagrams are accounted for by a model combining diffraction at the cavity edges and reflections from the substrate.
A novel approach to control the grain size of oxide thin film materials has been investigated. Perovskite BaTiO3 shows interesting grain structures when deposited on gold predeposited, (111)-oriented, singlecrystal SrTiO3 substrates. Solid oxide films grow epitaxially on patterned seed layers and show variations in grain size relative to the films deposited on SrTiO3 directly.
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