Yazar "Al, E. B." seçeneğine göre listele

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    Binding energies and optical absorption of donor impurities in spherical quantum dot under applied magnetic field
    (Elsevier, 2020) Al, E. B.; Kasapoglu, E.; Sakiroglu, S.; Sari, H.; Sokmen, I; Duque, C. A.
    In this study, we have calculated the binding energies of the ground-ls and first few excited impurity states such as 2s, 1p, 2p, ld, and 2d, as well as the wave functions and energies of an electron in spherical quantum dot which has finite confinement potential under applied magnetic field. Furthermore, we calculated the impurity related optical absorption coefficients for 1s -> 1p, 1p -> 2s, 2s -> 2p, 1p -> 1d, and 2p -> 2d transitions between higher impurity states than those available in the literature. The calculations have been made in the framework of the effective mass approximation via the diagonalization method by using the complete basis of functions obtained as the exact solutions of the infinite QD in the absence of the magnetic field. Considering the two-level approach, the optical response was treated in the density matrix expansion. The results show that the external magnetic field strongly affects the impurity binding energies in large dot radii and the optical absorption coefficients. Furthermore, it has been observed that the change of dot radius has a significant effect on the optical absorption coefficients.
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    Binding energy of donor impurity states and optical absorption in the Tietz-Hua quantum well under an applied electric field
    (ELSEVIER SCIENCE BV, 2018) Al, E. B.; Kasapoglu, E.; Sakiroglu, S.; Duque, C. A.; Sokmen, I.
    For a quantum well which has the Tietz-Hua potential, the ground and some excited donor impurity binding energies and the total absorption coefficients, including linear and third order nonlinear terms for the transitions between the related impurity states with respect to the structure parameters and the impurity position as well as the electric field strength are investigated. The binding energies were obtained using the effective-mass approximation within a variational scheme and the optical transitions between any two impurity states were calculated by using the density matrix formalism and the perturbation expansion method. Our results show that the effects of the electric field and the structure parameters on the optical transitions are more pronounced. So we can adjust the red or blue shift in the peak position of the absorption coefficient by changing the strength of the electric field as well as the structure parameters. (C) 2017 Elsevier B.V. All rights reserved.
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    Effects of applied electric and magnetic fields on the nonlinear optical properties of asymmetric GaAs/Ga1-xAlxAs double inverse parabolic quantum well
    (ELSEVIER SCIENCE BV, 2015) Al, E. B.; Ungan, F.; Yesilgul, U.; Kasapoglu, E.; Sari, H.; Sokmen, I.
    The combined effects of electric and magnetic fields on the optical absorption coefficients and refractive index changes related to the intersubband transitions within the conduction band of asymmetric GaAs/Ga1-xAlxAs double inverse parabolic quantum wells are studied using the effective-mass approximation and the compact density-matrix approach. The results are presented as a function of the incident photon energy for the different values of the electromagnetic fields and the structure parameters such as quantum well width and the Al concentration at the well center. It is found that the optical absorption coefficients and the refractive index changes are strongly affected not only by the magnitudes of the electric and magnetic fields but also by the structure parameters of the system. (C) 2015 Elsevier B.V. All rights reserved.
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    Effects of doping concentrations and position-dependent mass on the nonlinear optical properties of asymmetric double delta-doped GaAs quantum wells
    (Springer Heidelberg, 2024) Durmuslar, A. Salman; Al, E. B.; Althib, H. M.; Mora-Ramos, M. E.; Ungan, F.
    This study examines the electronic and optical properties of an asymmetric double delta doped quantum wells structure formed within GaAs. The electronic structure of system is obtained within effective mass and envelope wave function approximations. Optical responses are calculated in the framework of the compact density matrix approach. The roles of distance between wells, varying one well electron concentration, as well as length parameter of position-dependent mass, on the total optical absorption coefficients and the relative refractive index changes are investigated. The findings of this study indicate that prominence of optical coefficients occurs at higher energies for position-dependent mass, compared to constant mass case. Augmented right well electron concentrations lead to blue-shifts on the optical properties not only with constant mass but also with position-dependent mass. However, the increase in the wells' separation results the absorption peaks to move towards lower energies.
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    Effects of electric and magnetic fields on the electronic properties in the asymmetrical biconvex lens-shaped GaAs/GaAlAs quantum dots
    (Elsevier, 2024) Al, E. B.; Restrepo, R. L.; Morales, A. L.; Mora-Rey, F.; Sosa-Giraldo, T.
    Theoretical investigation of electronic properties in asymmetric biconvex lens -shaped GaAs/GaAlAs quantum dots is considered in the presence of the external magnetic and electric fields. In addition, the effects of the dot size and the asymmetry of the structure on the electronic properties are also investigated. The shape of this quantum dot corresponds to the intersection of two differently centered spheres. The energy levels and wave functions of the shallow hydrogenic impurity in the structure with a finite potential are calculated numerically in cylindrical coordinates with the effective mass approach using a complex eigenvalue formalism through a two-dimensional axisymmetrical and three-dimensional finite element methods. The results reveal significant dependence of the calculated physical properties on lens dimensions, axial impurity position, and intensities of applied electric and magnetic fields.
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    Effects of hydrostatic pressure, temperature, and position-dependent mass on the nonlinear optical properties of triple delta-doped GaAs quantum well
    (Springer Heidelberg, 2024) Tuzemen, A. Turker; Al, E. B.; Sayrac, H.; Dakhlaoui, H.; Mora-Ramos, M. E.; Ungan, F.
    In this study, we thoroughly investigate the impacts of hydrostatic pressure, temperature, and position-dependent mass (PDM) on the nonlinear optical properties of asymmetric triple delta-doped GaAs quantum wells. Our analysis covers total optical absorption coefficients, relative refractive index changes, nonlinear optical rectification, second harmonic generation, and third harmonic generation. Initially, we employ PDM to solve the time-independent Schr & ouml;dinger equation using the diagonalization method under effective mass and parabolic band approaches, considering pressure and temperature dependencies. Utilizing the first four energy eigenvalues and eigenfunctions, we apply the compact density matrix method to compute the system's nonlinear optical properties numerically. The results indicate a shift in optical property peak positions toward lower (higher) energy spectra with increasing hydrostatic pressure (temperature). Furthermore, the influence of PDM shifts the system's optical properties toward the higher energy spectrum, resembling the effect of temperature. From an experimental and theoretical perspective, one of the topics that researchers work on most is GaAs-based delta-doped systems (delta-doped heterojunction bipolar transistors, delta-doped field effect transistors, delta-multiple independent gate field effect transistors, etc.). We believe these findings will provide valuable insights for the researchers involved in GaAs-based delta-doped optoelectronic device design.
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    Effects of magnetic field, hydrostatic pressure and temperature on the nonlinear optical properties in symmetric double semi-V-shaped quantum well
    (SPRINGER, 2016) Yesilgul, U.; Ungan, F.; Al, E. B.; Kasapoglu, E.; Sari, H.; Sokmen, I.
    In this work, the effects of magnetic field, hydrostatic pressure and temperature on the linear and nonlinear optical properties in GaAs/AlxGa1-xAs symmetric double semi-V-shaped quantum well (DSVQWs) have been theoretically studied by using the compact-density matrix approach and the effective-mass approximation. Our numerical results show that the optical characteristic of these structures is strongly affected by the magnetic field, hydrostatic pressure and temperature.
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    Influence of hydrostatic pressure and temperature on the optical responses of asymmetric triple quantum wells
    (Springer Heidelberg, 2024) Durmuslar, A. Salman; Dakhlaoui, H.; Al, E. B.; Ungan, F.
    The work presents the effects of hydrostatic pressure and temperature on the electronic spectra as well as on the optical responses of parabolically shaped asymmetric triple quantum wells formed between the GaAs/Al0.3Ga0.7As heterostructures. The electronic structure of the configuration is obtained by iteratively solving the Schrodinger equation within effective mass and envelope wave function approximations. Optical properties are calculated within the compact density matrix approach framework. The results in this study show that increasing hydrostatic pressure field leads to small redshifts on the total optical absorption coefficient, relative refractive index change, nonlinear optical correction, and second and third harmonic generations, while temperature augmentation causes significant redshifts in these optical properties.
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    Infrared transitions between hydrogenic states in GaInNAs/GaAs quantum wells
    (WORLD SCIENTIFIC PUBL CO PTE LTD, 2016) Al, E. B.; Ungan, F.; Yesilgul, U.; Kasapoglu, E.; Sari, H.; Sokmen, I.
    The effects of nitrogen and indium concentrations on the 1s, 2s, 2p(0) and 2p +/--like donor impurity energy states in a single Ga1-xInxNyAs1-y/GaAs quantum well (QW) are investigated by variational approach within the effective mass approximation. The results are presented as a function of the well width and the donor impurity position. It is found that the impurity binding and transition energies depend strongly on the indium concentration while depends weakly on the nitrogen concentration.
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    Linear and nonlinear optical properties in an asymmetric double quantum well under intense laser field: Effects of applied electric and magnetic fields
    (ELSEVIER SCIENCE BV, 2016) Yesilgul, U.; Al, E. B.; Martinez-Orozco, J. C.; Restrepo, R. L.; Mora-Ramos, M. E.; Duque, C. A.; Ungan, F.; Kasapoglu, E.
    In the present study, the effects of electric and magnetic fields on the linear and third-order nonlinear optical absorption coefficients and relative change of the refractive index in asymmetric GaAs/GaAlAs double quantum wells under intense laser fields are theoretically investigated. The electric field is oriented along the growth direction of the heterostructure while the magnetic field is taken in-plane. The intense laser field is linear polarization along the growth direction. Our calculations are made using the effective-mass approximation and the compact density-matrix approach. Intense laser effects on the system are investigated with the use of the Floquet method with the consequent change in the confinement potential of heterostructures. Our results show that the increase of the electric and magnetic fields blue-shifts the peak positions of the total absorption coefficient and of the total refractive index while the increase of the intense laser field firstly blue-shifts the peak positions and later results in their red-shifting. (C) 2016 Elsevier B.V. All rights reserved.
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    Nonlinear optical properties of GaAs/AlGaAs asymmetric triple quantum wells designed for quantum cascade lasers: Effect of externally applied electric and magnetic fields
    (Elsevier, 2024) Tuzemen, A. Turker; Dakhlaoui, H.; Mora-Ramos, M. E.; Al, E. B.; Ungan, F.
    We explore the impact of external fields on the absorption coefficients and relative refractive index changes in a quantum cascade laser profile-like heterostructure that consists of a triple asymmetric quantum well. Firstly, we solve numerically the time -independent Schro dinger equation by using the diagonalization method under the effective mass and parabolic band approaches, to obtain the energy levels and wavefunctions. Then, we evaluate the optical coefficients from the analytical expressions derived from the compact density matrix method. The obtained results put forth that the resonant peaks of optical coefficients shift to higher (lower) energies by increasing the value of the electric (magnetic) field. These results indicate that it would be possible to adjust the optical properties of these structures to the desired range with external fields. As a result, we hope that new optoelectronic devices based on asymmetric triple quantum wells can be developed using the features found here.
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    The effects of temperature and pressure on optical properties of spherical core/shell/shell quantum dot
    (Indian Assoc Cultivation Science, 2024) Al, E. B.
    In this study, the effects of temperature and hydro-static pressure on the electronic and optical properties of the spherical core/shell/shell quantum dot structure is determined numerically. The energy eigenvalues of the system and their corresponding eigenfunctions are calculated using the diagonalization method within the framework of the effective mass approach. Then, linear, nonlinear and total intersubbands absorption coefficients and relative refractive index changes are calculated theoretically by iterative method within the framework of compact density matrix approach. With the results to be obtained from the study, it is predicted that this system can be recommended as a building block for various applications in the THz electromagnetic spectrum region.