The influence of a dielectric shell on metallic spherical nanoparticles [core-shell nanoparticles (CSNps)] in the resonant modal response of a surface plasmon resonance (SPR)-type sensor is presented. The planar multilayer sensor structure, based on the Kretschmann and surface plasmon coupled emission (SPCE) configurations, is coupled to a periodic array of these nanoparticles. In the first configuration, the CSNps are considered as a homogeneous layer with effective permittivity given by the Clausius-Mossotti mixing formula and polarizability of a core shell for a quasi-static scattering regime. In the second configuration, it performed an evaluation via the discrete complex image method (DCIM). Electromagnetic wave propagation is evaluated by the generalized reflection coefficient for multilayer structures. The analytical results are validated by numerical simulations performed via finite element method and also by experimental data. We observed that the dielectric shell thickness affects considerably the sensibility of the sensor when analyzing the change in other parameters of the CSNps array.Resonance 186

An alternative approach to classical surface plasmon resonance spectroscopy is dielectric-loaded waveguide (DLWG) spectroscopy, widely used in the past decades to investigate bio-interaction kinetics. Despite their wide application, a successful and clear approach to use the DLWGs for the one-step simultaneous determination of both the thickness and refractive index of organic thin films is absent in the literature. We propose here, for the first time, an experimental protocol based on the multimodal nature of DLWGs to be followed in order to evaluate the optical constants and thickness of transparent thin films with a unique measurement. The proposed method is general and can be applied to every class of transparent organic materials, with a resolution and accuracy which depend on the nature of the external medium (gaseous or liquid), the geometrical characteristics of the DLWG, and the values of both the thickness and dielectric constant of the thin film. From the experimental point of view, the method is demonstrated in a nitrogen environment with an accuracy of about 3%, for the special case of electroluminescent thin films of Eu3+β-diketonate complexes, with an average thickness of about 20 nm. The high value of the refractive index measured for the thin film with the Eu­(btfa)3(t-bpete) complex was confirmed by the use of a spectroscopic model based on the Judd–Ofelt theory, in which the magnetic dipole transition 5D0 → 7F1 (Eu3+) for similar films containing Eu3+ complexes is taken as a reference. The DLWGs are finally applied to control the refractive index changes of the organic thin films under UVA irradiation, with potential applications in dosimetry and monitoring light-induced transformation in organic thin films.

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This article presents an analysis of radiation and absorption properties of cylindrical gold nanodipoles in the transmitting mode. The conventional antenna theory and the linear method of moments are used for theoretical analysis of these antennas in the near-infrared and lower optical frequencies (1002500 THz). Frequency dependence of radiation and absorption parameters such as input impedance, efficiency, radiation, and loss resistance is calculated for different dipole's lengths and radii. The presented results can be useful to design efficient nanodipoles and to perform the input impedance matching of these antennas with plasmonic optical transmission lines.

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Resumo-Neste trabalhoé apresentada uma análise eletromagnética de um arranjo de nanoantenas sobre uma camada de grafeno depositada em um substrato SiO2. O grafenoé modelado como uma impedância superficial com condutividade descrita pelo modelo de Kubo. Os campos eletromagnéticos do arranjo periódico de nanoantenas foram determinados através da Função de Green Periódica, com condição de impedância na interface entre os meios. Nesta abordagem, as nanoantenas são modeladas como um arranjo periódico de nanodipolos sobre a camada de grafeno. Foram realizadas análises paramétricas dos campos elétrico e magnético, da densidade de corrente superficial sobre a camada de grafeno, e do diagrama de radiação de campo distante na estrutura. As simulações foram realizadas na frequência de 1,2THz, sendo verificadas as mudanças de campo próximo e distante em função da impedância superficial do Grafeno, controlada via potencial químico.Palavras-Chave-Arranjo planar, Impedância superficial, Grafeno, Funções de Green.Abstract-This paper presents an electromagnetic analysis of a nanoantenna array above a graphene layer deposited in a SiO2 substrate. Graphene is modeled as a surface impedance with conductivity described by the Kubo model. The electromagnetic fields of the nanoantenna array were determined by the Periodic Green's Function with impedance condition at the interface between the mediums. In this approach the nanoantenas are modeled like a periodic array of nanodipoles above the graphene layer. Parametric analyzes of the electric and magnetic fields, the surface current density on the graphene layer, and the far field radiation pattern were performed. The simulations were performed at the frequency of 1.2THz, and the near and far field changes were verified as a function of the surface impedance of the graphene, controlled by the chemical potential.

The present work describes the use of a simulation model based on asymptotic methods (ray tracing) on the propagation of ultra-wideband radio signals in a densely-arborized urban channel. The model was previously validated and adjusted using data obtained from measurement campaigns in the millimeter-wave band in locations different from the one to be analyzed here. The simulation uses deterministic methods to predict the received power, cross-polar discrimination, root mean square delay spread, and mean delay in a channel with a high density of scatterers (trees, buildings, and poles). Simulated signals were transmitted in the vertical and horizontal polarizations, considering non-specular reflections caused by rough surfaces and the effect of the transmitter's height variation in outdoor channels.