Papers by Keyword: Plasmons

Abstract: The current research work analysis the surface plasmons produced in the bimetallic thin films. The study aimed to understand the nature of surface plasmons produced from single metal thin film of copper and then to investigate the effect of addition of another metal thin layer above it. The research work was carried out via simulation analysis using Kretschmann-Raether configuration. Angular interrogation method and wavelength interrogation method was used to optimize the surface plasmon response from copper thin film in the nanometer range. On the optimized film of copper, another thin layer of gold and silver was added and nature of surface plasmons produced was analyzed. The results show better SPR response from Cu-Au and Cu-Ag bimetallic thin films than using single metal films. The reflected light intensity in the SPR response shows a drastic reduction from 15% to 5% for bimetallic Cu-Au thin film and to 2% for Cu-Ag thin film. The FWHM measurements also displays the reduction from 0.7724^o for Cu monometallic film to 0.4319^o for Cu-Au bimetallic films and 0.2460^o for Cu-Ag bimetallic thin film. The results obtained from this analysis certainly benefits the optical sensor applications in medical and biological fields.

Abstract: In recent years, the tunable plasmon modes in the terahertz region of a multilayer graphene structure interacting with a metallic film substrate have attracted significant interest motivated by the graphene´s unique optical and electronic properties and the possibility to enhance light-matter interaction. In this work, the plasmon waves in graphene layered systems on a conducting thin film are investigated, the hybrid graphene-metal metamaterialis surrounded by two semi-infinite materials with different dielectric constants ε₁andε₂, respectively. The dispersion relations of electronic collective excitations are calculated by the zeros of an effective dielectric constant obtained from a recursive relation for the amplitudes associated with the electric field between graphene layers in the metamaterial. Long-range Coulomb interactions based on the hybrid layered graphene-metal structure lead new set spectra of collective excitations. At long wavelength (q®0) the optical modes (w~q^1/2)depend on the two-dimensional carrier density, the metallic thickness, the metallic substrate plasmon frequency, the number of the graphene layers and the dielectric constants in which the hybrid graphene-metal structure is embedded. This latter plays an important role in a wide range of applications such as a surface plasmon resonance biological sensors and terahertz surface plasmons in optically pumped graphene metamaterials.

Abstract: A co-catalyst was synthesized by photochemically depositing Pd nanoparticles onto TiO₂ nanopowder support in a one-pot synthesis procedure. The Pd nanoparticles exhibited localised surface plasmon resonance observed using UV-VIS which increased the absorption cross-section of the co-catalyst system into the visible as well as UV regions of the spectrum. This was found to have a significant contribution to the photocatalytic activity of the catalyst in dye degradation experiments. The size, morphology and distribution of the Pd nanoparticles were determined by TEM, while the chemical state and amount of Pd deposited were analysed via XPS and ICP respectively.

Abstract: The technology problems of fabricating different, nanometers sized gold particles in the layered composites like light-sensitive chalcogenide glass/gold nanoparticles/transparent substrate or titanium/titanium oxide/gold nanoparticles were investigated in our work. Combination of ion implantation, plasma deposition with annealing processes results physical routes for creation of gold nanoparticles in the mentioned structures, which possess plasmon effects. These functionalized structures are planned to use for investigations of optical recording processes, biocompatibility of titanium implants.

Abstract: Optical and magneto-optical properties of GaMnSb layers fabricated on GaAs (001) substrates by laser ablation technique were studied using spectral ellipsometry (E =1.24-3.25 eV) and the transversal Kerr effect (TKE) (E = 0.5 4.2 eV) as well as atomic and magnetic force microscopy. Spectra of the constituents of the diagonal components of the permittivity tensor as well as TKE depended substantially on the layer fabrication conditions. At room temperature a strong resonant band was observed in the TKE spectra for the GaMnSb layers with low Mn content in the energy range E 0.5-1.5 eV. This resonant TKE band was explained by excitation of surface plasmons in MnSb nanoclusters, which arose during the growth of the layers. In the energy region E >1.5 eV the TKE spectra were related to interband transitions in MnSb inclusions.

Abstract: Graphene is a recently discovered new material with unique physical properties. In this paper we discuss its electrodynamic and optical properties. It is shown that the electromagnetic response of graphene to the external radiation is strongly nonlinear and such phenomena as the frequency harmonics generation and frequency mixing effects can be observed in it. The nonlinear susceptibility of graphene is higher than that of many other materials.We predict that under certain conditions the plasmon enhanced second harmonic generation can be observed in graphene.

Abstract: Optical and magneto-optical properties of In(Ga)MnAs layers fabricated by laser ablation on GaAs(100) substrates were studied. Spectra of the optical constants and the transversal Kerr effect (TKE) depended substantially on the conditions of layer fabrication and testified to the presence of MnAs inclusions in all the samples. The cross-sectional transmission electron microscopy revealed the presence in the layers of inclusions 10-40 nm in size. At room temperature, a strong resonant band was observed in the TKE spectra of some In(Ga)MnAs layers in the energy range 0.5-2.7 eV. The resonant character of the TKE spectra was explained by excitation of surface plasmons in the MnAs nanoclusters embedded in the semiconductor host.