Banca de DEFESA: EVERSON FRAZÃO DA SILVA

Uma banca de DEFESA de DOUTORADO foi cadastrada pelo programa.
STUDENT : EVERSON FRAZÃO DA SILVA
DATE: 22/07/2021
TIME: 10:00
LOCAL: Plataforma Google Meet
TITLE:

Absorption in Photonic Quasicrystals

KEY WORDS:

Absorption, Quasicrystals, Photonic Crystals, Octonacci, Dodecanacci, PT Symmetry, Graphenes.

PAGES: 90
BIG AREA: Ciências Exatas e da Terra
AREA: Física
SUMMARY:

After Yablonovitch's pioneering work (in 1987) on photonic crystals, 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. On the other hand, after Kohmoto's pioneering work
(also in 1987), the study of photonic quasi-crystals has been receiving a lot of attention. Photonic quasi-crystals exhibit long-
range order, non-translational symmetry and a characteristic in the auto-similarity optical spectra, a very interesting property in
fractal studies. In this doctoral thesis, we have study absorption and optical transmission spectra in multilayers, by using the
theory of photonic quasi-crystals. The technique that we use for the calculation of the optical spectrum is the technique of the
transfer matrix. The photonic quasi-crystals we studied are formed by the sequences of Octonacci and Dodecanacci. Also,
Graphenes are materials that have received a lot of attention for their optoelectronic properties, even in the absence of a band
gap. In this thesis we use graphene at the interfaces between the layers to obtain the spectra and compare the results with the
case without Graphenes. We also investigated the effect of the chemical potential for the control of band gaps in these
structures, as well as the influence of the oblique incidence. The study of coherent perfect absorption has been quite
highlighted also in recent years, mainly for several technological applications, such as modulators, Bragg reflectors, plasmon
structures, among others. On the other hand, Hermitian systems, previously present only in quantum mechanics, had their
studies expanded to acoustic and electronic systems. Non-Hermitian systems had their equivalent in optical systems where
what we call parity-time symmetry (PT symmetry) occurs, where the refractive indices of the material satisfy the condition n
(x) = n * (- x). In this thesis, we also calculated the transmission spectrum in a photonic crystal with PT symmetry, which are
formed by quasi-periodic sequences well known in the literature, namely: Fibonacci, Thue Morse and Double Period. In our
results, we have shown the existence of high transmission peaks as a result of the definition of PT symmetry in photonic quasi-
crystals.

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