• Comparative study of one-dimensional photonic crystal heterostructure doped with a high and low-transition temperature superconducting for a low-temperature sensor

      Soltani, A.; Ouerghi, F.; AbdelMalek, Fathi; Haxha, Shyqyri; University of Tunis-El Manar; University of Bedfordshire (Elsevier, 2019-04-20)
      In this work, we present a theoretical study dealing with the sensitivity to physical parameters such as defect nature and thickness, and temperature. Indeed, the sensitivity considerably enhanced via the use of one-dimensional photonic crystal heterostructure (1D-PCH) which is composed of a few layers of ordinary materials, and superconducting defects. The aim of this paper is to compare the sensitivity of two proposed models consisting of (a) 1D-PCH doped with a high-transition temperature superconductor (Yttrium barium copper oxide (YBCO)), and (b) 1D-PCH doped with a low-transition temperature superconductor (niobium nitrure (NbN)). By using the transfer-matrix method (TMM), it has been demonstrated that model (b) is very sensitive compared to model (a). Therefore, the superconducting defect nature on 1D-PCH, using a few layers can play a fundamental role in a very low-temperature sensor.
    • Effect of the elliptic rods orientations on the asymmetric light transmission in photonic crystals

      Soltani, A.; Ouerghi, F.; AbdelMalek, Fathi; Haxha, Shyqyri; Ademgil, Huseyin; Akowuah, Emmanuel K.; El-Manar University, Tunisia; University of Bedfordshire; European University of Lefke, Turkey; Kwame Nkrumah University of Science and Technology, Ghana (Elsevier, 2017-02-03)
      In this work, we report a novel design of a photonic crystal utilizing elliptic rods. The two-dimensional (2D) photonic crystal consists of an asymmetric distribution of unit cells to ensure the one-way transmission of light. Analysis performed indicated that the orientation of the ellipse along the major and minor axis has an influence on the shift of the transmission. In particular, this results in shift of the transmission towards high frequencies and subsequent oscillation of its magnitude. The peak of the transmission band was also found to be strongly influenced by the orientation angle, θ. It has been demonstrated that the strong asymmetric propagation properties of the proposed photonic crystal structure enables the switching of incident light from one direction to another. The proposed structure may be applied as a building block to integrated photonics applications.
    • Unidirectional light propagation photonic crystal waveguide incorporating modified defects

      Soltani, A.; Ouerghi, F.; AbdelMalek, Fathi; Haxha, Shyqyri; Ademgil, Huseyin; Akowuah, Emmanuel K.; Université de Tunis El Manar; University of Bedfordshire; European University of Lefke; Kwame Nkrumah University of Science and Technology (Elsevier GmbH, 2016-11-29)
      In this paper, we have proposed a design of an Optical Diode-like in two-dimensional (2D) Photonic Crystal (PC) waveguide. The proposed device consists of 2D square-lattice PC structures, and it is based on two PC waveguides with different symmetric guiding modes, where various configurations of defects, including elliptic or/and semi-circular defects have been incorporated. The proposed one-way light propagation Optical Diode has been designed and optimized by employing in-house 2D Finite Difference Time Domain (FDTD) numerical method. We have reported that the unidirectional light propagation depends strongly on the coupling region between the introduced defects and the adjacent waveguides, and it also depends on the matching and mismatching between the defects and waveguide modes. It has been shown also that owing to its tunable features, the proposed Optical Diode can be potentially applied as a building block in future complex optical integrated circuits.