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Abstract In the current work, the nonlinear optical properties in GaAs/Ga 1− x Al x As semiparabolic and parabolic quantum well(QW) with constant effective mass(CEM) and position dependent effective mass(PDEM) are estimated for different applied magnetic field. In this regard, we have obtained the analytical expressions of the nonlinear rectification(OR), second harmonic generation(SHG), third harmonic generation(THG), optical absorption coefficients(OACs), and refractive index changes(RICs) by using the compact density matrix formalism. Simultaneously, we obtain the reliable energy eigenvalues and their corresponding eigenfunctions via the finite difference method. According to the obtained results, it is found that: (1)the correct inclusion of PDEM is the cause of a noticeable difference in nonlinear optical properties with respect to the use of CEM. (2)the applied magnetic field bear substantial technological importance in the process of nonlinear optical properties modulation. Highlights • The nonlinear optical properties semiparabolic and parabolic QW with CEM and PDEM have been discussed. • We obtain the energy eigenvalues and their corresponding eigenfunctions via the fine difference method. • The effect of applied magnetic field B are also studied in their competition with CEM and PDEM. • Nanostructures possess considerably different behaviors under CEM and PDEM. [ABSTRACT FROM AUTHOR]

In this paper, we analytically study the effect of applied electric field on energy levels and optical properties of a Gaussian confinement quantum dot(QD). The second harmonic generation(SHG), linear and nonlinear optical absorption coefficients(OACs) have been obtained in the way of the compact density matrix and iterative approach. In the one electron approximation, we take into account all possible transition routes, which contribute to the SHG and OACs. The results show that the energy levels and nonlinear optical properties of the dot depend strongly on the applied electric field. Especially, the effects on the SHG and OACs are obviously different contributed by different transition routes. The overall results show that geometric parameters of the Gaussian confinement QD and applied electric field act a very important role in the electronic and optical properties of QD, which maybe play a vital role in related research fields. • We discuss the OACs and SHG of Gaussian QD with all optically allowed transitions. • We obtain the energy eigenvalues and eigenfunctions via the finite difference. • The effect of geometric structural factor and applied electric field are studied. • Nanostructures show completely different nonlinear optical behaviors. [ABSTRACT FROM AUTHOR]

In this study, the linear and nonlinear intersubband optical absorption coefficients (OACs) and refractive index changes (RICs) in GaAs/AlGaAs core/shell spherical quantum dots (QDs) are theoretically investigated within the framework of the compact-density-matrix approach and iterative method for both cases with and without on-center impurity. The energy eigenvalues and their corresponding eigenfunctions of the system are calculated by using the differential method. Our results show that the position and the magnitude of the resonant peaks of the nonlinear OACs and RICs depend strongly on the hydrogenic impurity and QDs radius. It was found that the total OACs indicates saturation at sufficiently high incident intensities. Also we found that the binding energy of the ground and excited states of the impurity depend on the QDs radius. [ABSTRACT FROM AUTHOR]

Abstract: The optical absorption coefficients and the changes in the refractive index in GaAs/AlGaAs parabolic quantum dots(QDs) with applied electric and magnetic fields are studied in detail. Analytical expressions for the linear and nonlinear intersubband absorption coefficients and refractive index changes are obtained by using a compact density matrix approach and an iterative procedure. Finally, the calculated results show the incident optical intensity, the frequencies of the confined potential of the QDs and the applied electric and magnetic fields have a great influence on the optical absorption coefficients and refractive index changes in this system. [Copyright &y& Elsevier]

Abstract: The optical rectification (OR) coefficient for cubical quantum dots (CQDs), with an applied electric field is theoretically investigated in the framework of the compact-density-matrix approach and an iterative method. The confined wave functions and energies of electrons in the CQDs are calculated in the effective-mass approximation. Numerical calculations are presented for typical GaAs/AlAs CQDs. The results show that the calculation for OR coefficient in the CQDs system can reach a magnitude of , two orders higher than that in the spherical quantum dots system. The OR coefficient strongly depends on the length of CQDs and the magnitude of electric field. And the peak shifts to the aspect of high energy when considering the electric field. [Copyright &y& Elsevier]

Abstract: The third-harmonic generation (THG) coefficient for cylindrical quantum dots in a static magnetic field is investigated theoretically. By using the compact density-matrix approach and the iterative method, we obtain an analytical expression for the THG coefficient, and numerical calculations for typical GaAs/AlAs cylindrical quantum dots are presented. The results show that the THG coefficient can reach a magnitude of 10−10 m2/V 2. In addition to the radius of the cylindrical quantum dots, both the parabolic confining potential and the static magnetic field have an influence on the THG coefficient. [ABSTRACT FROM AUTHOR]

Abstract: The second-harmonic generation (SHG) coefficient for cubical quantum dots (CQDs) with the applied electric field is theoretically investigated. Using the compact density-matrix approach and the iterative method, we get the analytical expression of the SHG coefficient. And the numerical calculations for the typical GaAs/AlAs CQDs are presented. The results show that the SHG coefficient can reach the magnitude of 10−5 m/V, about two orders higher than that in spherical quantum dot system. More importantly, the SHG coefficient is not a monotonic function of the length L of CQDs as well as the applied field F. If we select suitable values of F and L, we will get a higher value of the SHG coefficient. In addition, the relaxation rate also affects the SHG coefficient obviously. [ABSTRACT FROM AUTHOR]

In the present work, the effects of hydrostatic pressure, temperature, and magnetic field on the nonlinear optical rectification (OR) and second-harmonic generation (SHG) in asymmetrical Gaussian potential quantum well (QW) have been investigated theoretically. Here, the expressions for the optical properties are calculated by the compact-density-matrix approach and iterative method. Simultaneously, the energy eigenvalues and their corresponding eigenfunctions have been obtained by using the finite difference method. The energy eigenvalues and the shape of the confined potential are modulated by the hydrostatic pressure, temperature, and magnetic field. So the results of a number of numerical experiments indicate that the nonlinear OR and SHG strongly depends on the hydrostatic pressure, temperature, and magnetic field. This gives a new degree of freedom in various device applications based on the intersubband transitions of electrons. [ABSTRACT FROM AUTHOR]

Abstract: The second harmonic generation (SHG) in the asymmetric double triangular quantum wells (DTQWs) is investigated theoretically. The dependence of the SHG coefficient on the right-well width of the DTQWs is studied, and the influence of the applied electric field on SHG coefficient is also taken into account. The analytical expression of the SHG coefficient is analyzed by using the compact density-matrix approach and the iterative method. Finally, the numerical calculations are presented for the typical GaAs/Al x Ga1−x As asymmetric DTQWs. The results show that the calculated SHG coefficient in this coupled system can reach the magnitude of 10−5 m/V, 1–2 orders of magnitude higher than that in step quantum well, and that in double square quantum wells. Moreover, the SHG coefficient is not a monotonic function of the right-well width, but has complex relationship with it. The calculated results also reveal that an applied electric field has a great influence on the SHG coefficient. Applying an appropriate electric field to a DTQW with a wider right well can induce a sharper peak of the SHG coefficient due to the double-resonant enhancement. [Copyright &y& Elsevier]