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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 (A P) N / 2 / D / (A P) 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. [ABSTRACT FROM AUTHOR]

The conductance and electronic transmission of Dirac electrons and holes across multibarrier Cantor-like graphene are investigated using on the transfer matrix method and Landauer–Buttiker formalism. Electric and magnetic fields are applied to the top of a monolayer graphene to generate multiple electromagnetic barriers separated by quantum wells. The impact of the magnetic and electric fields as well as the quantum size on the behavior of the transmission coefficient and conductance is discussed. The results indicate that the transmission coefficients exhibit oscillations indicating the existence of resonant states in miniband energies separated by minigap energies. This phenomenon known as the bifurcation process is more pronounced for a higher number of barriers. The behavior observed in the conductance variation reflects of the transmission coefficient especially for lower energies. Furthermore, the contour plot of the transmission coefficient shows the predominant impact of the incidence angle on the symmetry of the minigaps and minibands. These results are expected to be beneficial for experiments that improve the performance of new generations of devices based on multibarrier Cantor-like graphene systems. [ABSTRACT FROM AUTHOR]

We present the first detailed study of optical absorption coefficients (OACs) in a GaAs quantum dot confined with a Woods–Saxon potential containing a hydrogenic impurity at its center. We use a finite difference method to solve the Schrödinger equation within the framework of the effective mass approximation. First, we compute energy levels and probability densities for different parameters governing the confining potential. We then calculate dipole matrix elements and energy differences, E 1 p − E 1 s , and discuss their role with respect to the OACs. Our findings demonstrate the important role of these parameters in tuning the OAC to enable blue or red shifts and alter its amplitude. Our simulations provide a guided path to fabricating new optoelectronic devices by adjusting the confining potential shape. [ABSTRACT FROM AUTHOR]

This paper addresses the problem of stabilization of non-minimum phase switched nonlinear systems where the internal dynamics with symmetries or non-symmetries of each mode may be unstable. The authors initially build a stabilizing Lyapunov controller for each mode in order to stabilize its own unstable internal dynamics. The proposed approach is based on the exact input-output feedback linearization technique and the Lyapunov stability theory. The stability results for non-minimum phase switched nonlinear systems with arbitrary switching rules are then obtained using generalized Gronwall–Bellman inequalities. Finally, numerical examples are provided to demonstrate the efficacy of the achieved results. [ABSTRACT FROM AUTHOR]

In this work, low terahertz (THz) spectroscopic properties of defective one-dimensional graphene-dielectric photonic crystal (1D-GPC) structure are theoretically investigated and analyzed in detail. The 1D-GPC is composed of a periodic stack of graphene nanolayers separated by isotropic dielectric slabs (SiO2), including an air defect as a central layer. The study is carried out using the well known transfer matrix method. Our numerical simulations showed that the suggested structure exhibits comb-like resonant peaks in the first transmission band of the 1D-GPC. These peaks are narrow, fully separated from each other and their number density increases by increasing the number of periods of the structure. Tunability of the optical characteristics of the device is also explored, taking into account the dependencies to the incidence angle, width, thickness, and refractive index of the dielectric layers, and the chemical potential of graphene sheets. Our calculations reveal that these transmission channels exhibit tunable behaviors against the parameters mentioned above. The observed spectroscopic features of the proposed structure make it an ideal candidate to realize tunable narrowband multichannel filters. [ABSTRACT FROM AUTHOR]

We theoretically investigate the optical response of one-dimensional graphene based photonic crystal (1D-GPC) structures with and without defect layer in the low terahertz (THz) frequency region. The 1D-GPC is composed of alternated layers of isotropic dielectric material (SiO2) and graphene monolayer sheets. Using the transfer matrix method (TMM), the effects of several parameters such as the incidence angle, width, thickness, and refractive index of the defect layer and the chemical potential of graphene sheets on the device response will be explored in detail for both TE and TM polarizations. Our simulation results indicate that when a defect layer is introduced, the structure may support two kinds of defect modes. One kind is created in the Bragg gap and the other one is created in the graphene-induced photonic band gap (GIPBG). Our results reveal that a defect mode can appear within the GIPBG only for an optical thickness of the defect layer greater than that of the alternated dielectric layers of the 1D-GPC. While, the defect modes in the Bragg gap may be created by simply breaking of the periodicity of the dielectric lattice. In addition, the resonance frequency of defect mode in the GIPBG is found to be almost insensitive to the incident angle for both polarizations. Moreover, we show that an effective Brewster angle for our structure can be deduced from the variation of the amplitude of defect mode with the incident angle. Our analysis has shown an innovative idea for the realization of tunable broadband reflectors and narrowband filtering devices. [ABSTRACT FROM AUTHOR]

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 Schrödinger-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. • We study the optical absorption coefficients in konwent-like quantum well. • The optical absorption coefficients and refractive index changes depend on the doping layer concentration and its location. • The self-consistent resolution is employed to compute the energy levels and wavefunctions. [ABSTRACT FROM AUTHOR]

We study the electronic and optical properties of a heterostructure based on Manning-like double quantum wells under the impact of an n-doped layer inserted in two different locations. By solving the coupled Schrödinger-Poisson equations, we have determined the four lowest energy levels and their corresponding density of probabilities. After that, we have deduced the optical absorption coefficients between the ground level and each excited state. The study addresses two locations of the doped layer. The first location is at the center of the heterostructure and the second one is at the middle of the right quantum well. The obtained findings show that the energy levels are degenerated when we dope at the center especially for low values of doping concentrations. However, by doping at the right well, we observe a lifting of degeneracy even for low concentrations of the doped layer. Our study demonstrated that the lifting of degeneracy which was absent for low concentrations in the case of doping at the center of the heterostructure can be obtained by adjusting one of the structural parameters of the Manning-like potential. Furthermore, we have discussed in detail the blue and red shifts behaviors observed in the dominant optical absorption coefficients, especially by varying the concentration of the doped layer. Our study confirms that the doping technique stills an excellent strategy to manipulate the electronic and optical properties in quantum wells based on symmetrical shapes. • We study the optical absorption coefficients in Manning double quantum wells. • The optical absorption coefficients depends on the doping layer concentration and its location. • The self-consistent resolution is employed to compute the energy levels and wavefunctions. [ABSTRACT FROM AUTHOR]

Abstract: Properties of the self-imaging effect based on multimode interference (MMI) in multimode photonic crystal waveguides (PCWs) are investigated and analyzed in detail. By combining photonic band gap (PBG) and total internal reflection (TIR) effects in PCWs, self-imaging phenomena are achieved for both TE and TM polarizations. To observe the images reproduced by this self-imaging phenomenon, finite-difference time-domain (FDTD) simulations are performed on a multi-mode PCW. From these numerical simulations the reproduced images are identified and their positions along the propagation axis are described. We also, present the design and simulation of novel polarization-insensitive power splitter and polarization splitter. The simulation results show that the optimized devices have excellent transmission efficiencies as well as wide operating frequency bandwidths and small structure size. So, the proposed devices are promising and may play an important role in high-density photonic integrated circuits in the future. [Copyright &y& Elsevier]

This paper reports the effect of Nickel (Ni) on indium sulfide (In2S3) powder. This work presents a systematic study of the physical and dielectric properties of In2-xS3Nix powders with 0, 2, 4, and 6 at.% of nickel. Doped and undoped samples were investigated by X-ray powder diffraction (XRD), energy dispersive X-ray spectroscopy, thermal gravimetric analysis, Fourier transform infrared (FTIR) spectroscopy, Raman spectroscopy, scanning electron microscopy (SEM), and impedance spectroscopy. XRD patterns revealed that each In2-xS3Nix composition was crystalline, which was also confirmed by the FTIR results. The presence of Ni in the samples was confirmed by energy dispersive spectroscopy (EDS). The Raman studies show different peaks related to the In2S3 phase and do not reveal any secondary phases of In–Ni and Ni–S. The SEM images of the undoped and Ni-doped In2S3 samples indicated a correlation between dopant content and the surface roughness and porosity of the samples. The impedance analysis indicated semiconductor behavior present in all samples, as well as a decrease in resistance with increasing Ni content. This work opens up the possibility of tailoring the properties and integrating Ni-doped In2S3 nanocomposites as thin film layers in future solar cells. [ABSTRACT FROM AUTHOR]

The broad acceptance of sustainable and renewable energy sources as a means of integrating them into electrical power networks is essential to promote sustainable development. Microgrids using direct currents (DCs) are becoming more and more popular because of their great energy efficiency and straightforward design. In this work, we discuss the control of a PV-based renewable energy system and a battery- and supercapacitor-based energy storage system in a DC microgrid. We describe a hierarchical control approach based on sliding-mode controllers and the Lyapunov stability theory. To balance the load and generation, a fuzzy logic-based energy management system has been created. Using a neural network, maximum power defects for the PV system were determined. The global asymptotic stability of the framework has been verified using Lyapunov stability analysis. In order to simulate the proposed DC microgrid and controllers, MATLAB/SimulinkR (2019a) was utilized. The outcomes show that the system operates effectively with changing production and consumption. [ABSTRACT FROM AUTHOR]