• Asymmetric transport of light in linearly arrayed metallic nano-particles

      Aroua, Walid; Horchani, R.; AbdelMalek, Fathi; Haxha, Shyqyri; Kamli, Ali A.; National Institute of Applied Science and Technology, Tunisia; Dhofar University; University of Bedfordshire; Jazan University, Saudi Arabia (Springer, 2016-09-15)
      A strong asymmetric light transport in a linear chain of spherical and equidistantly spaced silver metal nano-particles (MNPs) located near a substrate is reported. The contrast ratio of the proposed structure is above 0.95. We have studied the propagation of light in the array with respect to the metal and the size of the last nano-particle of the chain and the nature of the substrate. It is shown also that the presence of a copper or gold substrate enhance the guiding properties of the array. This structure opens the possibility to design various optical devices such as broadband antennae and optical diodes.
    • 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.
    • Light-switching-light optical transistor based on metallic nanoparticle cross-chains geometry incorporating Kerr nonlinearity

      AbdelMalek, Fathi; Aroua, Walid; Haxha, Shyqyri; Flint, Ian; National Institute of Applied Science and Technology, Tunisia; University of Bedfordshire; 3Selex ES Ltd, Luton (Wiley-VCH Verlag, 2016-06-13)
      In this research work, we propose all-optical transistor based on metallic nanoparticle cross-chains geometry. The geometry of the proposed device consists of two silver nanoparticle chains arranged along the x- and z-axis. The x-chain contains a Kerr nonlinearity, the source beam is set at the left side of the later, while the control beam is located at the top side of the z-chain. The control beam can turn ON and OFF the light transmission of an incoming light. We report a theoretical model of a very small all-optical transistor proof-of-conceptmade of optical ‘light switching light’concept. We show that the transmission efficiency strongly depends on the control beam and polarization of the incoming light. We investigate the influence of a perfect reflector and reflecting substrate on the transmission of the optical signal when the control beam is turned ON and OFF. These new findings make our unique design a potential candidate for future highly-integrated optical information processing chips.
    • 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.