Navegando por Orientadores "COSTA, Karlo Queiroz da"

Agora exibindo 1 - 14 de 14

Acesso aberto (Open Access)
Análise comparativa de nanoantenas plasmônicas no modo de recepção para a aplicação em nanocircuito óptico.
(Universidade Federal do Pará, 2020-01-30) LOPES, Patrik Coelho; COSTA, Karlo Queiroz da; http://lattes.cnpq.br/7932708321834647; https://orcid.org/0000-0003-4393-3217
In this work, a theoretical study is made for different cases of optical nanoantennas. Numerical analyzes are performed using the Finite Element Method (FEM). The first part of the analysis will be done with the isolated nanoantennas considered: dipole,dipole-loop, loop and rod-loop. Initially it is made for the transmission mode to obtain important parameters for the study of nanoantennas, such as input impedance, reflection coefficient, radiation efficiency and gain diagram. Later in reception mode, excited by a plane wave linearly polarized, varying the direction of polarization. Where the power received by charge versus frequency and the near-field electric are investigated for antennas. The results show that the case of the dipole-loop nanoantenna is the most efficient (reaching up to and er = 81.25%) in addition to a better reception band. The second part is presented the application of an optical nanocircuit, composed of the receiving loop connected to a bifilar Optical Transmission Line (OTL) with a dipole at the line end. Also investigated are the near-field and the received power for the nanocircuits analyzed separately, with a load at the terminal of the streaming. Finally, the excitation of the nanocircuit is done through an opening probe modeled by a gaussian beam, focused on the receiving loop, transferring energy to the emitting dipole, with a standing wave pattern, the electromagnetic coupling of the nanocircuit turns with the Gaussian beam, showed better results (with a maximum reached of PZC = −103 dBm) compared to the plane wave (with value maximum of PZC = −125 dBm), with the power received at the load of ZC = 50Ω.
Acesso aberto (Open Access)
Análise de nanoenlaces ópticos sem fio compostos por nanoantenas plasmônicas yagi-uda e dipolo
(Universidade Federal do Pará, 2019-12-17) GARCIA, Tiago dos Santos; COSTA, Karlo Queiroz da; http://lattes.cnpq.br/7932708321834647
This work shows a comparative theoretical analysis of plasmonic nanoantennas Yagi-Uda and dipole wireless optical nanolinks. All results found from the isolated antennas at transmission mode such as, input impedance, directivity, gain, radiation efficiency, reflection coeficiente and radiation diagram were obtained by the linear Method of Moments, assitionally, the effect of a silicon dioxide substract on antenna resonant properties were obtained by the Finite Element Method through COMSOL Multiphysics software. The numerical analysis of the nanolink is performed by the linear Method of Moments, witch the transmission power and the near electric field are investigated and optimized for the nanolinks Yagi-Uda/Yagi-Uda, Yagi-Uda/dipole and dipole/dipole. The results show that the Yagi-Uda/Yagi-Uda nanolinks offers an improvement in power transmission at some frequency points over the nanolinks dipole/dipole and Yagi-Uda/dipole. In addition, the results demonstrate that all three links can operate at good transmit power at different frequency points, varying the load impedance of the receiving antenna.
Acesso aberto (Open Access)
Análise de sensor plasmônico na configuração emissão acoplada via função de Green 3D
(Universidade Federal do Pará, 2018-09-28) CRUZ, André Felipe Souza da; DMITRIEV, Victor Alexandrovich; http://lattes.cnpq.br/3139536479960191; COSTA, Karlo Queiroz da; http://lattes.cnpq.br/7932708321834647
In the present work, a theoretical study on a plasmon resonance sensor in the Surface Plasmon Coupled Emission (SPCE) configuration is presented. Coupled to the sensor structure is a microfluidic channel containing suspended target particles (gold nanoparticles functionalized to attract fluorescent molecules), which when excited and immobilized upon the sensor structure can be efficiently modeled as a planar array of induced dipoles. The electromagnetic modeling of the device was performed by the magnetic potential, defined by means of the Periodic Green Function (PGF) 3D. The electromagnetic fields are presented in terms of the discrete spectral representation by the complex double Fourier series, and to reduce the number of terms in the series, it is proposed the use the Euler identity. Firstly, parametric field results are presented in the sensor structure, and then the spectral analysis of the magnetic potential field is performed, where the SPP and SW poles appear in the spectral domain. For the validation of the method, the limit case was analyzed, in which the particles are distant from each other, and compared with published works. Finally, results and discussions about the convergence of series in the cosine PGF are presented. The results show good agreement, showing that the theoretical method of PGF 3D is efficient, and can be used as a tool in the design of this sensing device.
Acesso aberto (Open Access)
Análise de sensores plasmônicos baseados em Nano estruturas estratificadas utilizando o Método das imagens complexas discretas
(Universidade Federal do Pará, 2018-05-11) SOUZA, Nadson Welkson Pereira de; COSTA, Karlo Queiroz da; http://lattes.cnpq.br/7932708321834647
In this thesis, the theoretical analysis of a surface plasmon resonance (SPR) sensor coupled to metallic nanoparticles is presented. The sensor is considered in the Surface Plasmon Coupled Emission (SPCE) configuration, where the metallic nanoparticles (or analytes) are modeled by equivalent dipoles located above the sensor. A complete set of Green’s dyadic functions for the electric field is estimated for planar, multilayer, and uniaxial media in a computationally efficient and convenient manner for applications using the Discrete Complex Imaging Method (DCIM) via the Generalized Pencil of Function Method (GPOF). The principle of complex path deformation in a two-level contour is employed to express an original integral as a sum of complex images. The results related to the surface plasmon resonance, reflection, near and far field of planar sensors are presented and it is described how these nanoparticles influence the ability to increase the near field strength and alter the sensitivity response of these optical sensors. In addition, for comparison purposes, some results are calculated by numerical and experimental methods. The results show suitable agreement, which proves that DCIM is an efficient and powerful theoretical method for analyzing SPR sensors in the SPCE configuration.
Acesso aberto (Open Access)
Análise de um sensor baseado em ressonância de superfície de plasma acoplado a um arranjo periódico de nanopartículas metálicas
(Universidade Federal do Pará, 2016-07-05) COSTA, Jefferson Souza; COSTA, Karlo Queiroz da; http://lattes.cnpq.br/7932708321834647
SPR sensors are photonic devices based on surface plasma resonance (SPR), which consists of longitudinal collective oscillation of free electron gas at the interface between a metal and a dielectric. Due to its surface stimuli sensitive response, the use of SPR sensors has been reported for various applications. In this paper, we evaluate an SPR sensor coupled to the periodic array of metal (gold) nanoparticles, which can represent the surface immobilization of metal nanopollutants generated, for example, from the nanocomposites manufacturing process. The the SPR sensor multilayer structure is compounded by a prism, a gold thin film and a SiO2 layer. The sensor response to variations in the nanoparticles array is theoretically analyzed by an analytical model based on the effective permittivity of Maxwell Garnett and the generalized reflection coefficient for planar multilayer structure. The analytical model is validated by comparison with experimental and numerical results, showing great accuracy for a given range of values of the periodic array parameters. The evaluation the allowed wave modes of the sensor structure and the multi-layer structure optimization, for the detection and characterization of static parameters of metal nanoparticles, are the main objectives of the analysis developed in this work.
Acesso aberto (Open Access)
Análise numérica de sensor de ressonância plasmônica de superfície baseado em grafeno na faixa de terahertz
(Universidade Federal do Pará, 2022-06-24) SILVA, Wêndria Cunha da; COSTA, Karlo Queiroz da; http://lattes.cnpq.br/7932708321834647
This work proposes a Terahertz plasmonic refraction index sensor based on Single-Layer Graphene operating as a refractometer in the Terahertz range. The configuration used is Kretschmann, where one of the variables that monitors the reflectivity is the chemical potential. The sensor was theoretically analyzed by the finite element method (FEM), using a bidimensional-based model structure. In it, the reflectivities and the field distributions were calculated for different parameters, such as sample thickness, operating frequency, incidence angle, chemical potential variation and electrical permittivity. Firstly, a study was made to determine the best operating frequency, the sensor’s angle of incidence and minimum sample thickness that the sample should have Subsequently, the numerical model was compared with the analytical model obtained through two literatures.. From the numerical results, parametric analyzes were performed to verify variations in sensitivity, full width at half maximum (FWHM) and resolution, all parameters of device quality. Numerical results are compared with theoretical concepts available in the literature and in recently published works.
Acesso aberto (Open Access)
Antena de grafeno composta de dipolo-espira para aumento da largura de banda
(Universidade Federal do Pará, 2017-02-17) AZEVEDO, Rodrigo Guimarães de; COSTA, Karlo Queiroz da; http://lattes.cnpq.br/7932708321834647
This work presents a graphene antenna composed by a planar dipole and a circular loop for increasing bandwidth in the terahertz range. The dipole is fed by a voltage source in its gap and the circular loop is a parasitic antenna without physical connection with dipole. The two-dimensional method of moments (MoM-2D) with surface impedance is used for numerical analysis of this antenna compound antenna. It is investigated the influence of geometry and the chemical potential of loop element on the input impedance and bandwidth of the dipole element, with objective to obtain broadband operation.
Acesso aberto (Open Access)
Combinação de antenas dipolo e espira para aplicações em banda larga em nanocircuito óptico
(Universidade Federal do Pará, 2015-12-18) SOUZA, Janilson Leão de; COSTA, Karlo Queiroz da; http://lattes.cnpq.br/7932708321834647
In this work, it is theoretically investigated the effect of broadband cylindrical nanoantenna in a plasmonic optical nanocircuit. The circuit is composed of a nanoantenna formed by the combination of loop and dipole antennas that is connected to a twowire optical transmission line in which only the electric dipole is connected to the line. The numerical analysis of the nanocircuit is done by the linear Method of Moments (MoM), where gold cylindrical conductors are modeled with a given surface impedance. The analysis is divided into two parts. In the first part, only the isolated nanoantenna is discussed, where the values of input impedance, current distribution, reflection coefficient, percentage bandwidth and radiated efficiency are investigated. Then, in the second part, the impedance matching of the nanocircuit is analyzed, presenting the results of current variation, planar distribution of the near field and the voltage reflection coefficient for different geometrical parameters. The results show that the loop inserted into the circuit increases the bandwidth of nanoantenna (with bandwidth of up to 42%) and decreases the overall voltage reflection coefficient of the optical nanocircuit (reaching up to -25dB).
Acesso aberto (Open Access)
Controle do diagrama de radiação de dipolo de grafeno pelo potencial químico
(Universidade Federal do Pará, 2018-12-13) PINTO, Gabriel Silva; COSTA, Karlo Queiroz da; http://lattes.cnpq.br/7932708321834647
This work presents a method of controlling the radiation diagram of a graphene dipole by the chemical potential. The dipole analyzed has rectangular geometry with power supply by voltage source in the center, where each arm of the dipole is maintained to a different chemical potential. The geometry is analyzed by the two-dimensional moments method (MoM-2D) in MATLABr software, with an equivalent surface impedance. Calculations of the main radiative properties of the antenna are presented as a function of the chemical potential. The results show that the greater the difference between the chemical potentials, the greater the displacement of the main lobe of the radiation diagram.
Acesso aberto (Open Access)
Desenvolvimento de um algoritmo computacional MoM 3D aplicado em nanoplasmônica
(Universidade Federal do Pará, 2012-12-13) SOUZA, Nadson Welkson Pereira de; COSTA, Karlo Queiroz da; http://lattes.cnpq.br/7932708321834647
This work presents the development of a computational algorithm for electromagnetic scattering analysis of isolated plasmonic nanostructures. The tridimensional Method of Moments (MoM-3D) was used to solve the electric field integral equation, and the Lorentz-Drude model was used to represent the complex permittivity of the metallic nanostructures. Based in this model, a computational algorithm written in C language was developed. As example of application and validation of the code, two classical electromagnetic scattering problems of metallic nanoparticles are analyzed: nanosphere and rectangular nanorod, where the spectral response and near-field distributions were calculated. The obtained results were compared with other models and a good agreement and convergence was observed.
Acesso aberto (Open Access)
Espalhamento eletromagnético no grafeno através de transformadas de impedância
(Universidade Federal do Pará, 2019-02-22) PIRES, Andrey Viana; COSTA, Karlo Queiroz da; http://lattes.cnpq.br/7932708321834647
Graphene is a two-dimensional material with good electrical properties that make possible new telecommunications applications in telecommunications on the terahertz range. This work presents an alternative analysis of the scattering problem in a graphene sheet using the impedance transform. The Green functions, electromagnetic fields and properties of the plasmonic surface wave on the graphene are demonstrated. The numerical results show the spatial field distributions and spectral analysis of the plasmonic wave as a function of media properties, frequency and chemical potential. The results show that the impedance transform is adequate for scattering analysis in graphene sheets because it uses the natural autofunctions of the problem.
Acesso aberto (Open Access)
Modelagem por MOM de um dipolo de grafeno com múltiplos potenciais químicos
(Universidade Federal do Pará, 2023-10-27) JESUS, Luiz Eduardo Moreira de; COSTA, Karlo Queiroz da; http://lattes.cnpq.br/7932708321834647
In this dissertation, the potential of graphene in the terahertz frequency range was explored, particularly its ability to control the radiation pattern and impedance of a graphene dipole antenna by varying the chemical potential in multiple controllable segments. Two dipole antennas were analyzed, one with four graphene segments and another with six graphene segments, where each segment can have its chemical potential controlled directly. The study used the Method of Moments with graphene surface impedance values to calculate input impedance, gain, surface current distribution, and radiation pattern. The variations in chemical potentials were divided into symmetric and asymmetric groups, allowing adjustments to the second resonance and the angle of maximum gain in the radiation pattern, respectively. Compared to four-segment antennas, the six-segment antenna exhibited increased gain in the symmetric group with little variation in the second resonance. Furthermore, the gain of the six-segment antennas showed a notable increase at the point of maximum deviation while maintaining nearly constant angular displacement. This study paves the way for highly adjustable and efficient graphene antennas with promising applications in communication technology and radiation. Future work may explore various chemical potentials, other antenna geometries, and optimization techniques in simulation.
Acesso aberto (Open Access)
Nanoantena Óptica Plasmônica Dipolo-Espira de Banda Larga
(Universidade Federal do Pará, 2018-10-11) SOUZA, Janilson Leão de; COSTA, Karlo Queiroz da; http://lattes.cnpq.br/7932708321834647
Acesso aberto (Open Access)
Otimização de nanoantenas plasmônicas para células solares orgânicas
(Universidade Federal do Pará, 2016-01-18) SILVA JÚNIOR, Marcelino Lopes Corrêa da; DMITRIEV, Victor Alexandrovich; http://lattes.cnpq.br/0684541646225359; COSTA, Karlo Queiroz da; http://lattes.cnpq.br/7932708321834647
This work shows a theoretical nanoantennas study about organic solar cells of thin films, occasioning the increase in the efficiency of light absorption. The unitary organic solar cell formed by a reflector silver block, an active layer formed by the semiconductor P3HT:PCBM and a nanoantenna, also made of silver. The numerical analysis of the device is made through the Finite Element Method; the materials are analysed from the relative permittivity. Firstly, we executed the validation of the nanostructure through the numerical method. Then, we apply the geometric optimization process in the other nanoantenna models. This optimization process was based on nanoantennas geometrical parameters preserving its superficial area. Since were considered four new models of nanoantennas with different geometrical parameters, which means, conical nanoantennas, root cone, and exponential root cone 1 and 2. It was observed, from the efficiency of integrated absorption for different incidence angles and light polarization, current density and plasmonic decay that the nanoantennas, the root cone and the exponential cone 2, gave better performance compared to the other models.