Yazar "Sari, H." seçeneğine göre listele
Listeleniyor 1 - 20 / 100
Sayfa Başına Sonuç
Sıralama seçenekleri
Öğe A theoretical study on the optical properties of a quantum well with short-range bottomless exponential potential(World Scientific Publ Co Pte Ltd, 2019) Ungan, F.; Mora-Ramos, M. E.; Sakiroglu, S.; Sari, H.; Sokmen, I.The effects of external applied fields on the electron-related optical nonlinear properties in a short-range bottomless exponential potential quantum well are investigated. The potential profile behaves as inverse square root in the vicinity of the origin and vanishes exponentially toward infinity, supporting a finite number of bound states whose energies and wave functions are determined within the effective-mass approximation. The linear, third-order nonlinear and total optical absorption coefficients (TOACs) as well as the coefficient of relative refractive index changes (RRICs) of the system are calculated from the expressions derived in the framework of the compact density matrix approach. The results obtained after numerical calculations show that with the effect of the static electric and magnetic fields (high-frequency THz laser field), the resonant peak position of the optical response shifts toward higher (lower) energies and the magnitude of the peak increases.Öğe 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.Öğe Binding energies of donor impurities in modulation-doped GaAs/AlxGa1-xAs double quantum wells under an electric field(ACADEMIC PRESS LTD- ELSEVIER SCIENCE LTD, 2009) Kasapoglu, E.; Ungan, F.; Sari, H.; Sokmen, I.In this study, we have investigated theoretically the binding energies of shallow donor impurities in modulation-doped GaAs/Al0.33Ga0.67 As double quantum wells (DQWs) under an electric field which is applied along the growth direction for different doping concentrations as a function of the impurity position. The electronic structure of modulation-doped DQWs under an electric field has been investigated by using a self-consistent calculation in the effective-mass approximation. The results obtained show that the carrier density and the depth of the quantum wells in semiconductors may be tuned by changing the doping concentration, the electric field and the structure parameters such as the well and barrier widths. This tunability gives a possibility of use in many electronic and optical devices. (C) 2009 Elsevier Ltd. All rights reserved.Öğe Binding energy and optical absorption of donor impurity states in "12-6" tuned GaAs/GaAlAs double quantum well under the external fields(ELSEVIER SCIENCE BV, 2019) Kasapoglu, E.; Sakiroglu, S.; Sari, H.; Sokmen, I; Duque, C. A.We have investigated the binding energies of the s-symmetric ground and first excited shallow donor impurity states and the total 1s -> 2s absorption coefficient, including the first and third order corrections, in "12-6" tuned GaAs/GaAlAs double quantum well as a function of the impurity position, size of the structure, and the electric and magnetic field intensities. The obtained results show that the electronic and optical properties of tuned GaAs/GaAlAs double quantum well can be adjustable by an appropriate choice of the sample geometry, material parameters and applied external fields which will lead to new potential applications in optoelectronics.Öğe Binding energy of impurity states in an inverse parabolic quantum well under magnetic field(ELSEVIER SCIENCE BV, 2007) Kasapoglu, E.; Sari, H.; Sokmen, I.We have investigated the effects of the magnetic field which is directed perpendicular to the well on the binding energy of the hydrogenic impurities in an inverse parabolic quantum well (IPQW) with different widths as well as different Al concentrations at the well center. The Al concentration at the barriers was always x(max) = 0.3. The calculations were performed within the effective mass approximation, using a variational method. We observe that IPQW structure turns into parabolic quantum well with the inversion effect of the magnetic field and donor impurity binding energy in IPQW strongly depends on the magnetic field, Al concentration at the well center and well dimensions. (c) 2006 Elsevier B.V. All rights reserved.Öğe Combined effects of intense laser field and applied electric field on exciton states in GaAs quantum wells: Transition from the single to double quantum well(WILEY-V C H VERLAG GMBH, 2012) Duque, C. A.; Mora-Ramos, M. E.; Kasapoglu, E.; Sari, H.; Sokmen, I.The effects of intense laser radiation on the exciton states in GaAs-Ga1xAlxAs quantum wells are studied with the inclusion of applied dc electric fields oriented along the growth direction of the system. The calculations are made within the effective mass and parabolic band approximations. The intense laser effects have been included along the lines of the Floquet method, modifying the confinement potential associated to the heterostructure. The results for the exciton binding energy, the energy of the exciton-related photoluminescence peak, and the carriers overlap integral are presented for several configurations of the quantum well size, the strength of the applied electric fields, and the incident laser radiation.Öğe Combined effects of intense laser field, electric and magnetic fields on the nonlinear optical properties of the step-like quantum well(ELSEVIER SCIENCE SA, 2015) Kasapoglu, E.; Duque, C. A.; Mora-Ramos, M. E.; Restrepo, R. L.; Ungan, F.; Yesilgul, U.; Sari, H.; Sokmen, I.In the present work, the effects of the intense laser field on total optical absorption coefficient (the linear and third-order nonlinear) and total refractive index change for transition between two lower-lying electronic levels in the step-like GaAs/Ga1-xAlxAs quantum well under external electric and magnetic fields are investigated. The calculations were performed within the compact density-matrix formalism with the use of the effective mass and parabolic band approximations. The obtained results show that both total absorption coefficient and refractive index change are sensitive to the well dimensions and the effects of external fields. By changing the intensities of the electric, magnetic and non-resonant intense laser fields together with the well dimensions, we can obtain the blue or red shift, without the need for the growth of many different samples. (C) 2015 Elsevier B.V. All rights reserved.Öğe Combined effects of the intense laser field, electric and magnetic fields on the optical properties of n-type double delta-doped GaAs quantum well(ELSEVIER SCIENCE BV, 2017) Sari, H.; Kasapoglu, E.; Sakiroglu, S.; Yesilgul, U.; Ungan, F.; Sokmen, I.In the present work, the effects of the non-resonant intense laser field, electric and magnetic fields on the optical properties, such as linear, third order nonlinear and the total optical absorption coefficient and refractive index changes associated with the intersubband transitions between the ground and the first excited states in the n-type double delta-doped GaAs quantum well is theoretically studied by solving the Schrodinger equation in the laser-dressed confinement potential within the framework of effective mass approximation. The analytical expressions of the linear and third-order nonlinear optical absorption coefficients and refractive index changes are obtained by using the compact-density matrix formalism. Our numerical results show that the optical absorption coefficient and refractive index change are quite sensitive to the applied external fields, such as non resonant intense laser field, electric and magnetic fields. The obtained results can be applied for the design of various optoelectronic devices based on the intersubband transitions of electrons.Öğe Density of impurity states of hydrogenic impurities in an inverse parabolic quantum well under the magnetic field(ELSEVIER SCIENCE BV, 2007) Kasapoglu, E.; Sari, H.; Sokmen, I.We investigated the effects of the magnetic field on the density of impurity states in a GaAs/GaAlAs inverse parabolic quantum well (lPQW) for different Al concentrations at the well center. The calculations were performed within the effective mass approximation, using a variational method. We report in this paper the effects of the magnetic field, well width and the Al concentration at the well center on the density of states and the binding energies of the donor impurities. (c) 2006 Elsevier B.V. All rights reserved.Öğe Dependence of impurity binding energy on nitrogen and indium concentrations for shallow donors in a GaInNAs/GaAs quantum well under intense laser field(SPRINGER, 2011) Ungan, F.; Kasapoglu, E.; Sari, H.; Sokmen, I.Within the framework of the effective-mass approximation, using a variational method, we have calculated the effect of intense laser radiation on the binding energy of the shallow-donor impurities in a Ga1-xInxNyAs1-y/GaAs single quantum well for different nitrogen and indium mole concentrations. Our numerical results show that the binding energy strongly depends on the laser intensity and frequency (via the laser dressing parameter) and it also depends on the nitrogen and indium concentrations. Impurity binding energy under intense laser fields can be tuned by changing the nitrogen and indium mole fraction.Öğe Donor impurity states and related optical responses in triangular quantum dots under applied electric field(ACADEMIC PRESS LTD- ELSEVIER SCIENCE LTD, 2014) Kasapoglu, E.; Ungan, F.; Sari, H.; Sokmen, I.; Mora-Ramos, M. E.; Duque, C. A.The linear and nonlinear coefficients for the optical absorption and relative refractive index change associated with transitions between donor impurity states in a two-dimensional quantum dot of triangular shape under applied electric field are calculated for y-polarization of the incident light. Both the effective mass and parabolic band approximations have been considered. The results show that the application of a DC electric field strengthens the impurity-related optical absorption response, with particular relevance in the case of the nonlinear contribution to it. However, for a fixed donor atom position inside the triangular quantum dot, the calculations show that the in-plane orientation of the applied field can becomes a critical parameter that may lead to a strong quenching of the interstate light absorption. (C) 2014 Elsevier Ltd. All rights reserved.Öğe Effect of applied external fields on the nonlinear optical properties of a Woods-Saxon potential quantum well(ELSEVIER SCIENCE BV, 2019) Ungan, F.; Mora-Ramos, M. E.; Yesilgul, U.; Sari, H.; Sokmen, IIn this present work a detailed theoretical study on the influence of the static electric, magnetic, and nonresonant intense THz laser fields on the nonlinear optical properties such as nonlinear optical rectification (NOR) and second harmonic generation (SHG), of a quantum well that has the Woods-Saxon potential profile. The static electric and high-frequency intense THz laser fields are applied along the growth-direction of the structure whilst the static magnetic field is applied perpendicular to them. The outcome of the numerical calculation demonstrates that, both the peak potions of the NOR and SHG coefficients exhibit a blue-shift with the increment of the static electric and magnetic fields, but their peak amplitudes increases with the magnitude of the electric field whilst decreases with the magnitude of the magnetic field. However, the peak positions of the NOR and SHG coefficients exhibit firstly a blue-shift, and then a red-shift with the increment of the laser intensity, but their peak amplitudes increases. We hope that these theoretical results will be useful for designing new optoelectronic devices with a performance tailored by the adjustment of the applied fields.Öğe The effect of hydrostatic pressure on subband structure and optical transitions in modulation-doped quantum well(ACADEMIC PRESS LTD- ELSEVIER SCIENCE LTD, 2011) Ungan, F.; Yesilgul, U.; Sakiroglu, S.; Kasapoglu, E.; Sari, H.; Sokmen, I.Within the framework of effective-mass approximation, we have calculated theoretically the effects of hydrostatic pressure and doping concentration on subband structure and optical transitions in modulation-doped GaAs/Al(x)Ga(1-x)As quantum well for different well widths. The electronic structure of modulation-doped quantum well under the hydrostatic pressure is determined by solving the Schrodinger and Poisson equations self-consistently. The results obtained show that intersubband transitions and the subband energy levels in the modulation-doped quantum well can be significantly modified and controlled by the well width, donor concentration and hydrostatic pressure. (C) 2011 Elsevier Ltd. All rights reserved.Öğe Effect of intense high-frequency laser field on the linear and nonlinear intersubband optical absorption coefficients and refractive index changes in a parabolic quantum well under the applied electric field(ELSEVIER SCIENCE BV, 2014) Yesilgul, U.; Ungan, F.; Sakiroglu, S.; Mora-Ramos, M. E.; Duque, C. A.; Kasapoglu, E.; Sari, H.; Sokmen, I.The effects of the intense high-frequency laser field on the optical absorption coefficients and the refractive index changes in a GaAs/GaAlAs parabolic quantum well under the applied electric field have been investigated theoretically. The electron energy levels and the envelope wave functions of the parabolic quantum well are calculated within the effective mass approximation. Analytical expressions for optical properties are obtained using the compact density-matrix approach. The numerical results show that the intense high-frequency laser field has a large effect on the optical characteristics of these structures. Also we can observe that the refractive index and absorption coefficient changes are very sensitive to the electric field in large dimension wells. Thus, this result gives a new degree of freedom in the optoelectronic device applications. (C) 2013 Elsevier B.V. All rights reserved.Öğe The effect of intense laser field on the photoionization cross-section and binding energy of shallow donor impurities in graded quantum-well wire under an electric field(IOP PUBLISHING LTD, 2006) Kasapoglu, E.; Sari, H.; Yesilgul, U.; Sokmen, I.The laser-field dependence of the impurity binding energy and donor-related photoionization cross-section in graded quantum-well wire under an external static electric field is calculated by a variational method and in the effective mass approximation. We have shown that, in the graded quantum-well wire structures, not only the 'dressed' potential but also the applied direction of the external electric field plays a very important role in the determination of the binding energy.Öğe The effect of nitrogen on the diamagnetic susceptibility of a donor in GaxIn1-xNyAs1-y/GaAs quantum well under the magnetic field(ACADEMIC PRESS LTD- ELSEVIER SCIENCE LTD, 2010) Kilicarslan, E.; Sakiroglu, S.; Kasapoglu, E.; Sari, H.; Sokmen, I.The binding energy and diamagnetic susceptibility of a hydrogenic donor in a GaxIn1-xNyAs1-y/GaAs quantum well has investigated in the presence of the magnetic field by using a trial wave function in the framework of the effective mass approximation. The results show that the diamagnetic susceptibility and binding energy of the donor in the GaxIn1-xNyAs1-y/GaAs quantum well increases with nitrogen mole fraction. Also, we concluded that the incorporation of several percent of nitrogen in GaxIn1-xAs alloy causes a larger band gap difference between the well and barrier and therefore deeper quantum well, resulting in the stronger confinement of the donor electron and hence the smaller separation between the electron and impurity atom. (C) 2010 Elsevier Ltd. All rights reserved.Öğe The effect of the intense laser field on the electronic states and optical properties of n-type double delta-doped GaAs quantum wells(ELSEVIER SCIENCE BV, 2017) Kasapoglu, E.; Yesilgul, U.; Ungan, F.; Sokmen, I.; Sari, H.In this work, within the effective mass approximation we have performed a theoretical study of electronic states, the intersubband-related optical absorption coefficient and relative refractive index change properties in the GaAs-based double delta-doped quantum well under non-resonant intense laser field. By solving the Schrodinger equation in the laser-dressed confinement potential, We calculated eigenvalues and corresponding eigenfunctions as an intense laser parameter. We concluded that the separation between ground and first excited energy levels in the double delta-doped quantum well increases in energy by the increase of the laser field intensity and this effect leads to an optical blue-shift in intersubband transitions. Therefore a significant tunability of the optical transitions in double delta-doped quantum well can be achieved by modulating the intensity of the intense laser field. (C) 2016 Elsevier B.V. All rights reserved.Öğe The effect of the intense laser field on the electronic states I and optical properties of n-type double delta-doped GaAs quantum wells (vol 64, pg 82, 2017)(ELSEVIER SCIENCE BV, 2018) Kasapoglu, E.; Yesilgul, U.; Ungan, F.; Sokmen, I.; Sari, H.…Öğe The effect of the intense laser field on the intersubband transitions in Ga1-xInxNyAs1-y/GaAs single quantum well(ELSEVIER SCIENCE BV, 2011) Ungan, F.; Kasapoglu, E.; Duque, C. A.; Sari, H.; Sokmen, I.The effect of the intense laser field on the intersubband optical absorption for (1-2) transition in a Ga1-xInxNyAs1-y/GaAs single quantum well for different nitrogen and indium concentrations is investigated. The numerical calculations are performed in the effective-mass approximation. We have found that the increase of the nitrogen and indium concentrations with intense laser field leads to important effects on the optical properties of a quantum well. The obtained results show that the desired energy range corresponding to the subbands may be tuned by changing the laser intensity and the nitrogen and indium concentrations. This tunability gives a possibility for near-infrared electro-absorption modulators and quantum well infrared detectors. (C) 2011 Elsevier B.V. All rights reserved.Öğe Effects of an in-plane magnetic field on the energy dispersion, spin texturing and conductance of double quantum wires(ACADEMIC PRESS LTD- ELSEVIER SCIENCE LTD, 2016) Gisi, B.; Karaaslan, Y.; Sakiroglu, S.; Kasapoglu, E.; Sari, H.; Sokmen, I.We investigate the electronic structure, spin and transport properties of double quantum wires formed by a symmetric, double quartic-well potential subjected to an in-plane magnetic field by taking into account Rashba and Dresselhaus spin-orbit couplings. The energy dispersion relation of the system is analyzed for different strengths of spin-orbit interactions, magnitude and direction of magnetic field. Our numerical results reveal that the existence of aforementioned parameters modifies strongly the energy band structure, introduces a wave vector dependence to energies and also leads to crossings and anticrossings between subbands. This complex structure of energy dispersion gives rise to the appearance of square-wave like oscillations in the conductance. The spin-orbit couplings, magnetic field, potential profile and Fermi energy of an electron significantly affect the depth and width of conductance steps. Moreover, we found that the competing effect between spin-orbit couplings and magnetic field leaves its marks on the spin texturing. (C) 2015 Elsevier Ltd. All rights reserved.
