Navegando por Autor "Brandão, E. R."
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Artigo Octonacci photonic crystals with negative refraction index materials(Elsevier, 2016-12) Anselmo, Dory Hélio Aires de Lima; Brandão, E. R.; Vasconcelos, Manoel Silva deWe investigate the optical transmission spectra for s-polarized (TE) and p-polarized (TM) waves in onedimensional photonic quasicrystals on a quasiperiodic multilayer structure made up by alternate layers of SiO2 and metamaterials, organized by following the Octonacci sequence. Maxwell's equations and the transfer-matrix technique are used to derive the transmission spectra for the propagation of normally and obliquely incident optical fields. We assume Drude-Lorentz-type dispersive response for the dielectric permittivity and magnetic permeability of the metamaterials. For normally incident waves, we observe that the spectra does not have self-similar behavior or mirror symmetry and it also features the absence of optical band gap. Also for normally incident waves, we show regions of full transmittance when the incident angle qC ¼ 0 in a particular frequency range.Artigo Octonacci photonic quasicrystals(Elsevier, 2015-05-09) Anselmo, Dory Hélio Aires de Lima; Brandão, E. R.; Costa, C. H.; Vasconcelos, Manoel Silva de; Mello, V. D.We study theoretically the transmission spectra in one-dimensional photonic quasicrystals, made up of iO2(A) and TiO2(B) materials, organized following the Octonacci sequence, where the nth-stage of the multilayer Sn is given by the rule Sn ¼ Sn1Sn2Sn1, for n P 3 and with S1 ¼ A and S2 ¼ B. The expression for transmittance was obtained by employing a theoretical calculation based on the transfer-matrix method. For normally incident waves, we observe that, for a same generation, the transmission spectra for transverse electric (TE) and transverse magnetic (TM) waves are equal, at least qualitatively, and they present a scaling property where a self-similar behavior is obtained, as an evidence that these spectra are fractals. The spectra show regions where the omnidirectional band gaps emerges for specific generations of Octonacci photonic structure, except to TM waves. For TE waves, we note that all of them have almost the same width, for different generations. We also report the localization of modes as a consequence of the quasiperiodicity of the heterostructureArtigo Photonic band gap spectra in Octonacci metamaterial quasicrystals(Elsevier, 2017) Brandão, E. R.; Vasconcelos, Manoel Silva de; Albuquerque, Eudenilson Lins de; Fulco, Umberto LaicoIn this work we study theoretically the photonic band gap spectra for a one-dimensional quasicrystal made up of SiO2 (layer A) and a metamaterial (layer B) organized following the Octonacci sequence, where its nth-stage Sn is given by the inflation rule Sn ¼ Sn1Sn2Sn1 for n 3, with initial conditions S1 ¼ A and S2 ¼ B. The metamaterial is characterized by a frequency dependent electric permittivity εðuÞ and magnetic permeability mðuÞ. The polariton dispersion relation is obtained analytically by employing a theoretical calculation based on a transfer-matrix approach. A quantitative analysis of the spectra is then discussed, stressing the distribution of the allowed photonic band widths for high generations of the Octonacci structure, which depict a self-similar scaling property behavior, with a power law depending on the common in-plane wavevector kx