Enhancement of transmission in 1D thermal tunable metallic photonic crystal filter with exponential gradation thickness
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THE EUROPEAN PHYSICAL JOURNAL D
Regular Article
Enhancement of transmission in 1D thermal tunable metallic photonic crystal filter with exponential gradation thickness Zeinab Zarea and Abdolrasoul Gharaati Department of Physics, Payame Noor University, Tehran 19395-4697, Iran Received 28 January 2020 / Received in final form 17 April 2020 Published online 1 July 2020 c EDP Sciences / Societ`
a Italiana di Fisica / Springer-Verlag GmbH Germany, part of Springer Nature, 2020 Abstract. Using the transfer matrix method, the transmission of 1D thermal tunable metallic photonic crystal (PC) filter with symmetry exponential gradation of thickness has been examined in this article. For the purpose of making this structure, three different materials silicon, silica, and silver have been used. The refractive index of silver is considered as a function of temperature and wavelength. The dependence of the silicon refractive index on the wavelength is also considered in calculations. The effect of the variation of temperature and incident angle on the transmission peaks has been investigated. By increasing the temperature, the transmission peaks in the position of defect modes move toward the larger wavelength at a given incident angle. When the incident angle is increased, however, they shift toward the shorter wavelength in both polarizations. The height of transmission peaks decreases linearly by increasing the temperature. Results are compared with those obtained in our previous work. The position of the transmission peaks in the structure with the exponential gradation of thickness is higher than the non-graded and linear graded, and the transmission peaks are sharper in TE polarization.
1 Introduction Photonic crystals (PCs) are periodic micro or nano structures with different dielectric constants which are arranged periodically [1–6]. The spatially periodic distribution of dielectric constant of these structures can lead to the unique property of them called photonic bandgaps [7]. An electromagnetic wave with a resonant frequency dropping in to the photonic bandgap cannot propagate in such structures and reflected totally within the photonic bandgap [8–13]. Using ternary photonic crystals can enlarge the photonic band gap which has been more functional compared with binary photonic crystals [14]. These structures have been used in the design of filters or refractometric applications [15]. In order to control the light propagation, PCs can be used in different applications such as optical fibers [6], waveguides [16], cavities [17], sensors [18], filters [19–21], and medical applications [22]. Introducing the disorder which is a kind of structural defect can confine electromagnetic waves with in a certain resonant frequencies around the defect position so the localized states can be created within the photonic band gaps [23,24]. This property can be used to design optical filters. Tunable PC devices are very important due to control the band gaps [25,26]. An optical filter which makes tunable PCs can be tuned by adjust
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