1,426 research outputs found
Surface scattering contribution to the plasmon width in embedded Ag nanospheres
Nanometer-sized metal particles exhibit broadening of the localized surface
plasmon resonance (LSPR) in comparison to its value predicted by the classical
Mie theory. Using our model for the LSPR dependence on non-local surface
screening and size quantization, we quantitatively relate the observed plasmon
width to the nanoparticle radius and the permittivity of the surrounding
medium . For Ag nanospheres larger than 8 nm only the non-local
dynamical effects occurring at the surface are important and, up to a diameter
of 25 nm, dominate over the bulk scattering mechanism. Qualitatively, the LSPR
width is inversely proportional to the particle size and has a nonmonotonic
dependence on the permittivity of the host medium, exhibiting for Ag a maximum
at . Our calculated LSPR width is compared with recent
experimental data.Comment: 11 pages, 4 figures. Accepted for publication in Optics Expres
Diffuse Surface Scattering in the Plasmonic Resonances of Ultra-Low Electron Density Nanospheres
Localized surface plasmon resonances (LSPRs) have recently been identified in
extremely diluted electron systems obtained by doping semiconductor quantum
dots. Here we investigate the role that different surface effects, namely
electronic spill-out and diffuse surface scattering, play in the optical
properties of these ultra-low electron density nanosystems. Diffuse scattering
originates from imperfections or roughness at a microscopic scale on the
surface. Using an electromagnetic theory that describes this mechanism in
conjunction with a dielectric function including the quantum size effect, we
find that the LSPRs show an oscillatory behavior both in position and width for
large particles and a strong blueshift in energy and an increased width for
smaller radii, consistent with recent experimental results for photodoped ZnO
nanocrystals. We thus show that the commonly ignored process of diffuse surface
scattering is a more important mechanism affecting the plasmonic properties of
ultra-low electron density nanoparticles than the spill-out effect.Comment: 19 pages, 5 figures. Accepted for publication in The Journal of
Physical Chemistry Letter
Effect of aminoacylation on tRNA conformation.
Translational diffusion coefficients have been simulated for various conformations of tRNAPhe (yeast) by bead models, in order to analyze data obtained by dynamic light scattering on the free and the aminoacylated form. The 18% increase of the translational diffusion coefficient upon deacylation, reported by Potts et al. (1981), could not be represented by any change of the L-hinge angle, but could only be simulated by a conformation change to an extended form with extensive dissociation of base pairs. Since extensive unpairing is not consistent with evidence accumulated in the literature, the change of the diffusion coefficient must be mainly due to processes other than intramolecular conformational changes
Realizing strong light-matter interactions between single nanoparticle plasmons and molecular excitons at ambient conditions
Realizing strong light-matter interactions between individual 2-level systems
and resonating cavities in atomic and solid state systems opens up
possibilities to study optical nonlinearities on a single photon level, which
can be useful for future quantum information processing networks. However,
these efforts have been hampered by the unfavorable experimental conditions,
such as cryogenic temperatures and ultrahigh vacuum, required to study such
systems and phenomena. Although several attempts to realize strong light-matter
interactions at room-temperature using so-called plasmon resonances have been
made, successful realizations on the single nanoparticle level are still
lacking. Here, we demonstrate strong coupling between plasmons confined within
a single silver nanoprism and excitons in molecular J-aggregates at ambient
conditions. Our findings show that the deep subwavelength mode volumes, ,
together with high quality factors, , associated with plasmons in the
nanoprisms result in strong coupling figure-of-merit -- as high as
~m -- a value comparable to state-of-art
photonic crystal and microring resonator cavities, thereby suggesting that
plasmonic nanocavities and specifically silver nanoprisms can be used for
room-temperature quantum optics
Plasmonic glasses: Optical properties of amorphous metal-dielectric composites
Plasmonic glasses composed of metallic inclusions in a host dielectric medium are investigated for their optical properties. Such structures characterized by short-range order can be easily fabricated using bottom-up, self-organization methods and may be utilized in a number of applications, thus, quantification of their properties is important. We show, using T-Matrix calculations of 1D, 2D, and 3D plasmonic glasses, that their plasmon resonance position oscillates as a function of the particle spacing yielding blue-and redshifts up to 0.3 eV in the visible range with respect to the single particle surface plasmon. Their properties are discussed in light of an analytical model of an average particle's polarizability that originates from a coupled dipole methodology
Bi-metal coated aperture SNOM probes
Aperture probes of scanning near-field optical microscopes (SNOM) offer resolution which is limited by a sum of the aperture diameter at the tip of a tapered waveguide probe and twice the skin depth in metal used for coating. An increase of resolution requires a decrease of the aperture diameter. However, due to low energy throughput of such probes aperture diameters usually are larger than 50 nm. A groove structure at fiber core-metal coating interface for photon-to-plasmon conversion enhances the energy throughput 5-fold for Al coated probes and 30-fold for Au coated probes due to lower losses in the metal. However, gold coated probes have lower resolution, first due to light coupling from the core to plasmons at the outside of the metal coating, and second due to the skin depth being larger than for Al. Here we report on the impact of a metal bilayer of constant thickness for coating aperture SNOM probes. The purpose of the bilayer of two metals of which the outer one is aluminum and the inner is a noble metal is to assure low losses, hence larger transmission. Using body-of-revolution finite-difference time-domain simulations we analyze properties of probes without corrugations to measure the impact of using a metal bilayer and choose an optimum bi-metal configuration. Additionally we investigate how this type of metalization works in the case of grooved probes
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