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    Harnessing a Dielectric/Plasma Photonic Crystal as an Optical Microwave Filter: Role of Defect Layers and External Magnetic Fields
    (Mdpi, 2024) Dakhlaoui, Hassen; Belhadj, Walid; Elabidi, Haykel; Al-Shameri, Najla S.; Ungan, Fatih; Wong, Bryan M.
    We investigate the transmittance spectrum of a multichannel filter composed of dielectric (A) and plasma (P) materials in the microwave region within the transfer matrix formalism. Two configurations of the proposed filter are studied under the influence of an applied magnetic field: (1) a periodic structure containing (A/P)N unit cells surrounded by air and (2) the introduction of a second dielectric material (D) acting as a defect layer to produce an (AP)N/2/D/(AP)N/2 structure. Our findings reveal that in the periodic case, the number of resonant states of the transmittance increases with number N; however, the observed blue and red shifts depend on the intensity and orientation of the applied magnetic field. We present contour plots of the transmission coefficients that show the effect of the incident angle on the shifts of the photonic band gaps. Furthermore, we find that the introduction of a defect layer generates additional resonant states and merges the central resonant peak into a miniband of resonances. Moreover, we show that the number of resonant peaks and their locations can be modulated by increasing the unit cell number, N, as well as increasing the width of the inserted defect layer. Our proposed structures enable the design of novel photonic filters using magnetized plasma materials operating in the microwave region.
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    Linear and nonlinear optical properties in GaAs quantum well based on konwent-like potential: Effects of impurities and structural parameters
    (Elsevier, 2023) Dakhlaoui, Hassen; Belhadj, Walid; Ungan, Fatih; Al-Shameri, Najla S.
    The optical absorption coefficients (OACs), refractive index changes (RICs), and electronic states in konwent-like quantum well under the effects of silicon impurities were studied within the framework of the effective mass approximation (EMA). Firstly, the subband energy levels and their probability densities are determined by solving Schrodinger-Poisson equations iteratively. Once these quantities are computed, we have addressed different OACs and RICs (linear and nonlinear) between the ground and the first excited levels. We have considered two positions of the silicon-doped layer. The first one is at the center of the structure and the second one is inside the left potential well. Our findings indicate that in the case of doping at the center, an increase in the concentration of the doped layer reduces the energy levels of the ground and the first excited states. However, when the doped layer is moved to the left well, its concentration increase augments the energy of the first excited state and diminishes that of the ground state. This behavior of energy levels and wavefunctions is attributed to the newly created triangular well around the doped layer. Moreover, the impact of the structural parameters and their impact on the red/blue shift of the (OACs) and (RICs) have been discussed in detail. As a consequence, the concentration and position of the doped layer as well as the structural parameters constitute an important tool to modify the shape of the confining potential which leads to additional control of the energy states and optical properties of different heterostructures based on konwent-like quantum wells.