Karlo Costa

By Karlo Costa and Victor Dmitriev

Part of the book: Ultra Wideband Communications

By Karlo Queiroz da Costa, Janilson Leão Souza and Victor Dmitriev

An impedance matching analysis of two plasmonic nanocircuits connected to cylindrical nanoantennas is presented. In the first case, a bifilar optical transmission line (OTL) with finite length is connected between two nanodipoles, where one is illuminated by an optically focused Gaussian beam (receiving dipole) and the other radiates energy received from the OTL (emitting dipole). In the second case, the OTL is fed by a voltage source on one side and connected to a dipole‐loop composed antenna on the other side. These circuits are analysed electromagnetically by the linear method of moments (MoM) with equivalent surface impedance of conductors. Some results are compared using the finite element method. The results show the impedance matching characteristics of the circuits as a function of their geometries and the broadband response of the second circuit due the broadband dipole‐loop antenna.

Part of the book: Nanoplasmonics

By Nadson Welkson Pereira de Souza, Jefferson Souza Costa, Rafael Correa dos Santos, André Felipe Souza da Cruz, Tommaso Del Rosso and Karlo Queiroz da Costa

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.

Part of the book: Resonance

By Karlo Queiroz da, Gleida Tayanna Conde de, Gabriel Silva Pinto and Andrey Viana Pires

Graphene possesses good properties as unusually high electron mobility, atomic layer thickness, and unique mechanical flexibility, which made it one promising material in the design of terahertz antennas. In this book chapter, we present a numerical analysis of a broadband dipole-loop graphene antenna for application in terahertz communications. The bidimensional method of moments (MoM-2D), with equivalent surface impedance of graphene, is used for numerical analysis. First, we review the principal characteristics of the conventional rectangular graphene dipole. Then, we consider the broadband graphene antenna, composed by one rectangular dipole placed near and parallel to a circular-loop graphene element, where only the dipole is feed. In this analysis, we investigated the effects of the geometrical parameters and the chemical potential, of the graphene material, on the overall characteristics of the compound antenna. Some results are compared with simulations performed with software based on finite element method. The results show that this simple compound graphene antenna can be used for broadband communications in the terahertz band.

Part of the book: Antennas and Wave Propagation

By Karlo Queiroz da Costa, Gleida Tayanna Conde de Sousa, Paulo Rodrigues Amaral, Janilson Leão Souza, Tiago Dos Santos Garcia and Pitther Negrão dos Santos

In this work, we present a theoretical analysis of wireless optical nanolinks formed by plasmonic nanoantennas, where the antennas considered are Yagi-Uda and cylindrical nanodipoles made of Au. The numerical analysis is performed by the finite element method and linear method of moments, where the transmission power and the near electric field are investigated and optimized for three nanolinks: Yagi-Uda/Yagi-Uda, Yagi-Uda/dipole and dipole/dipole. The results show that all these case can operate with good transmission power at different frequencies by adjusting the impedance matching in the transmitting antennas and the load impedance of the receiving antennas.

Part of the book: Nanoplasmonics