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    Calculation of the changes in the absorption and refractive index for intersubband optical transitions in a quantum box
    (WILEY-V C H VERLAG GMBH, 2005) Karabulut, I; Unlu, S; Safak, H
    Analytic forms of the changes of the absorption and refractive index associated with intersubband optical transitions in a quantum box are obtained by using the compact density matrix approach. Numerical results are presented for a typical AlGaAs/GaAs quantum box system. The linear, third-order nonlinear, and total refractive-index and absorption changes are examined as a function of the incident optical intensity. The results obtained show that the incident optical intensity has a great effect on the total absorption and refractive-index changes.
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    Comment on "Electric field effect on the second-order nonlinear optical properties of parabolic and semiparabolic quantum wells"
    (AMER PHYSICAL SOC, 2005) Karabulut, I; Atav, U; Safak, H
    Zhang and Xie [Phys. Rev. B 68, 235315 (2003)] presented their results for the second harmonic generation (SHG) susceptibility in electric-field-biased parabolic and semiparabolic quantum wells (QW's). In this Comment, we demonstrate that the results presented for the SHG coefficient in a parabolic QW with an applied electric field are not physically sound and they contradict with well-established properties of the Hermite polynomials which just happen to be the wave functions describing such a system. It is shown that in a parabolic QW with an applied electric field intersubband transitions contribute to neither second nor any higher order harmonic generation.
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    Nonlinear optical rectification in asymmetrical semiparabolic quantum wells
    (PERGAMON-ELSEVIER SCIENCE LTD, 2005) Karabulut, I; Safak, H; Tomak, M
    The optical rectification in a semiparabolic quantum well is theoretically investigated. The electronic states in a semiparabolic quantum well are calculated exactly, within the envelope function and the displaced harmonic oscillator approach. The nonlinearity resulting from the asymmetry of the confining potential is studied in the lowest order. The numerical results for the typical AlxGa1-xAs/GaAs material show that the large optical rectification coefficient decreases with increasing confining potential frequency of the semiparabolic quantum well. Moreover, the optical rectification coefficient also depends sensitively on the relaxation rate of semiparabolic quantum well system. (C) 2005 Elsevier Ltd. All rights reserved.
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    Nonlinear optical rectification in semiparabolic quantum wells with an applied electric field
    (ELSEVIER SCIENCE BV, 2005) Karabulut, I; Safak, H
    The optical rectification (OR) in a semiparabolic quantum well with an applied electric field has been theoretically investigated. The electronic states in a semiparabolic quantum well with an applied electric field are calculated exactly, within the envelope function and the displaced harmonic oscillator approach. Numerical results are presented for the typical AlxGa1-xAs/GaAs quantum well. These results show that the applied electric field and the confining potential frequency of the semiparabolic quantum well have a great influence on the OR coefficient. Moreover, the OR coefficient also depends sensitively on the relaxation rate of the semiparabolic quantum well system. (c) 2005 Elsevier B.V. All rights reserved.