Papers by António Danucha Baptista Baptista
IEEE Photonics Journal
Nano antennas have a significant role in photonic nanodevices due to the ability of concentrating... more Nano antennas have a significant role in photonic nanodevices due to the ability of concentrating radiation in a small space region. The confined fields present a high sensitivity to the used materials in that regions. The electromagnetic wave models of nanoantennas usually operate in the frequency domain. However, electromagnetic wave models in the time domain are just as important and more advantageous, for example, in light pulses propagation. In this article, a new stochastic method based on the ray model of light in absorbing media is presented and light patterns on a target near a nanoantenna are obtained. The optical properties of the materials are described by their complex refractive index. When dealing with photons in the time domain, this formulation allows the calculation of the probability of a given photon movement. Different patterns, obtained with the new method, are compared with a Finite Element Tool ones, leading to model validation. The simulated structure included an aperture nanoantenna. With this method, the results show the light confinement and the extraordinary optical transmission phenomenon, meaning some photons on the target are refracted and re-transmitted by the metal. Thus, the output beam is more intense than the transmitted directly by the apertures. Index Terms-Extraordinary optical transmission, light patterns, nano arrays, nano antennas, optical devices. I. INTRODUCTION N OWADAYS, nanotechnology is an emergent area with several applications. For example, optical devices such as nano arrays or nanoantennas are commonly used in photonic circuits. The physical principle is based on light-matter interaction [1], [2], [3], [4]. The classical theories, assuming that metals reflect all incident light, can adequately represent light-metal interaction for radio and microwave frequencies. However, they no longer apply to optical frequencies and at nano scale. In 1998, Ebbesen discovered a new optical phenomenon, named extraordinary optical transmission (EOT), which is a resonant
IEEE Photonics Journal
At nano-scale new phenomena have been discovered, allowing devices' miniaturisation, energy harve... more At nano-scale new phenomena have been discovered, allowing devices' miniaturisation, energy harvesting, and power reduction. The Extraordinary Optical Transmission (EOT) phenomenon was reported in 1998 by Ebessen, who stated that the resonant peaks in the response of metallic nano antennas were more intense than predicted by classical diffraction theories. Years later, the main reason for this behaviour was attributed to the Surface Plasmon Polaritons (SPP), at least in ultraviolet and visible regions. In this article, a new method to model the radiation-matter interaction on a dielectric-metal interface is proposed, based on Maxwell's equations and Fresnel Coefficients in absorbing media. Transmission percentage, angle and propagation length are obtained for a rigorous sweep on incident angle and wavelength. The results taken using some noble metals allow us to observe the presence of surface phenomena at expected SPP resonances. First, it is noticeable huge values of transmission in ultraviolet and visible regions, meaning that the metal does not reflect all the radiation. Also, the transmission angle tends to be higher, meaning huge surface components. Furthermore, the transmission length is on orders of 50-100 nm, meaning that phenomena as EOT only occurs at the nano-scale, since waves should arrive at another interface before being absorbed.
Nos dias de hoje, o uso de satelites e essencial na vida quotidiana e afeta quase todos os campos... more Nos dias de hoje, o uso de satelites e essencial na vida quotidiana e afeta quase todos os campos de atividade da sociedade. Na Defesa, as comunicacoes por satelite tem um papel preponderante: a possibilidade de obter informacao sobre as atividades do inimigo e sobre o teatro de operacoes em tempo real, e vital para o sucesso de qualquer missao. A maioria das ligacoes intersatelites, e entre os satelites e a estacao de base, usa a banda de radiofrequencia (RF). As comunicacoes oticas sao uma tecnologia emergente que oferece, entre outras vantagens, maior largura de banda, que e necessaria para poder transmitir um volume crescente de dados. Este facto representa uma mais-valia significativa para as operacoes militares. O futuro das comunicacoes por satelite esta pois, dependente dos desenvolvimentos nos sistemas de comunicacao oticos. Neste artigo, o diagrama de blocos e as principais caracteristicas destes sistemas serao apresentadas e analisadas.
Nanomaterials, 2021
In the last decade, the development and progress of nanotechnology has enabled a better understan... more In the last decade, the development and progress of nanotechnology has enabled a better understanding of the light–matter interaction at the nanoscale. Its unique capability to fabricate new structures at atomic scale has already produced novel materials and devices with great potential applications in a wide range of fields. In this context, nanotechnology allows the development of models, such as nanometric optical antennas, with dimensions smaller than the wavelength of the incident electromagnetic wave. In this article, the behavior of optical aperture nanoantennas, a metal sheet with apertures of dimensions smaller than the wavelength, combined with photovoltaic solar panels is studied. This technique emerged as a potential renewable energy solution, by increasing the efficiency of solar cells, while reducing their manufacturing and electricity production costs. The objective of this article is to perform a performance analysis, using COMSOL Multiphysics software, with differen...
Applied Sciences, 2020
At the end of the XX century, a new phenomenon was discovered by Ebbesen, the extraordinary optic... more At the end of the XX century, a new phenomenon was discovered by Ebbesen, the extraordinary optical transmission. He reported that metallic arrays composed of nano holes, also called nanoantennas, can support resonant optical transmissions responsible by the amplification and concentration of electromagnetic radiation. Classical diffraction theories do not predict this extraordinary phenomenon. This article shows the timeline of theories that try to model the interaction between light and metal planes with slits, holes, grooves or apertures. The comparison between theories is done. Furthermore, as the optical response of these nanoantennas is dependent on the complex dielectric function, there is a high probability of successfully using these structures as sensors. This article aimed to verify how the structure parameters (periodicity, hole diameter, nanoantenna thickness and substrate thickness) can influence the optical response in order to tune the spectrum. Using a Finite Elemen...
Chemosensors, 2020
Currently, huge opportunities for the inclusion of new optical devices in our lives have been app... more Currently, huge opportunities for the inclusion of new optical devices in our lives have been appearing. There are evident and irrefutable examples for nanoantenna applications. They can be used to improve already developed devices or even be used as the device. In both cases, they can be applied in diverse areas, such as medicine, environment, energy, defense, and communications. A square arrayed metallic nanoantenna composed of circular holes is studied by performing simulations using COMSOL Multiphysics. This article aims to study the influence of the nanoantenna’s metal, silver, gold, copper and aluminum, but also the optical response dependence on the nanoantenna’s periodicity, its thickness, the hole diameter, and the number of holes. It is evidenced that the optical response can be tuned using the structure parameters and by choosing an appropriate material. This tuning will allow developers to fulfil the specifications, since it is proven that the response peak can be delibe...
Information, 2018
In the present paper, a smart planar electrically steerable passive array radiator (ESPAR) antenn... more In the present paper, a smart planar electrically steerable passive array radiator (ESPAR) antenna was developed and tested at the frequency of 1.33 GHz with the main goal to control the main radiation lobe direction, ensuring precise communication between the antenna that is implemented in an unmanned aerial vehicle (UAV) and the base station. A control system was also developed and integrated into the communication system: an antenna coupled to the control system. The control system consists of an Arduino, a digital potentiometer, and an improved algorithm that allows defining the radiation-lobe direction as a function of the UAV flight needs. The ESPAR antenna was tested in an anechoic chamber with the control system coupled to it so that all previously established requirements were validated.
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Papers by António Danucha Baptista Baptista