Absorção em quasi-cristais fotônicos

• Ano de defesa: 2021
• Autor(a) principal: Silva, Everson Frazão da
• Tipo de documento: Tese
• Tipo de acesso: Acesso aberto
• Idioma: por
• Instituição de defesa: Universidade Federal do Rio Grande do Norte; Brasil; UFRN; PROGRAMA DE PÓS-GRADUAÇÃO EM FÍSICA
• Palavras-chave em Português: Física; Absorção; Quasi-cristais; Cristais fotônicos; Grafenos
• Link de acesso: https://repositorio.ufrn.br/handle/123456789/44656

After Yablonovitch's pioneering work on Photonic Crystals [1], there was a growing interest in studies on the propagation of electromagnetic waves in periodic multilayers. Mainly because of the possibility of guiding, allowing or prohibiting the propagation of light in certain frequency bands with the use of band gaps (PBGs). On the other hand, after Kohmoto's pioneering work [2], the study of photonic quasi-crystals has received a lot of prominence. The photonic quasi-crystals exhibit long-range order, nontranslational symmetry and a characteristic in the self-similarity optical spectra [3], a very interesting property in fractal studies. In this doctoral thesis, we will approach a study on the spectrum of absorption and optical transmission in multilayers, using the theory of photonic quasi-crystals. The technique that we will use for the calculation of the optical spectrum will be the technique of the transfer matrix. The photonic quasi-crystals that we will study will be formed by the sequences of Octonacci and Dodecanacci. Graphenes are materials that have received a lot of attention for their optoelectronic properties, even in the absence of a band gap. We intend to use graphene at the interfaces between the layers to obtain the spectra and compare the results without graphenes. We will also investigate the e ect of the chemical potential for the control of band gaps in these structures, as well as the in uence of the oblique incidence. The study of perfect coherent absorption (ACP) has received a lot of prominence in recent years, mainly for several technological applications, such as modulators [4], Bragg re ectors [5], plasmonic structures [6], among others. On the other hand, Hermitian systems, previously present only in quantum mechanics, had their studies expanding to acoustic and electronic systems. Non-Hermitian systems had their equivalent in optical systems where what we call the parity-time symmetry (PT symmetry) occurs, where the material's refractive indices satisfy n(x) = n∗(−x). We calculated the transmission spectrum in a photonic crystal with PT symmetry, formed by known quasi-periodic sequences: Fibonacci, Thue Morse and Double Period. In these structures, high transmission peaks arise due to the use of PT symmetry.