The effects of quantum dot (QD) radius, incident light intensity, temperature and other factors on the optical absorption coefficients (OACs) of cylindrical QDs are investigated numerically for typical GaAs/Ga[Formula: see text]Al[Formula: see text]As. We theoretically studied the cylindrical QDs with like-inversely quadratic Hellmann potential and parabolic potential. The expressions for the energy levels and wave functions were obtained by the Nikiforov–Uvarov method, and then the expressions for the OACs were derived by using the density matrix theory and the iterative method. Finally, the results show that the structural and external parameters affect the sensitivity of the optical absorption properties by influencing the matrix elements and energy levels, and the quantum confinement effects affect their applicable frequencies, which makes the QD system easier to tune.
The effects of quantum dot (QD) radius, incident light intensity, temperature and other factors on the optical absorption coefficients (OACs) of cylindrical QDs are investigated numerically for typical GaAs/Ga[Formula: see text]Al[Formula: see text]As. We theoretically studied the cylindrical QDs with like-inversely quadratic Hellmann potential and parabolic potential. The expressions for the energy levels and wave functions were obtained by the Nikiforov–Uvarov method, and then the expressions for the OACs were derived by using the density matrix theory and the iterative method. Finally, the results show that the structural and external parameters affect the sensitivity of the optical absorption properties by influencing the matrix elements and energy levels, and the quantum confinement effects affect their applicable frequencies, which makes the QD system easier to tune.
In this present study, we have theoretically investigated the effect of applied external electric field and non-resonant intense laser field, as well as the adjustable physical parameters (A, M, and η) of the system, on the linear and nonlinear of GaAs/GaAlAs cylindrical quantum dot. The confinement potential of the quantum dot is composed of the axial potential with a Razavy-type quantum well in the z-direction, and the cylindrical-type potential in the radial direction. To achieve this goal, the wave functions, and the corresponding eigenvalues of the electron are investigated by resolving the time-independent Schrödinger equation using the diagonalisation technique in terms of the effective mass approximation. The linear and nonlinear optical properties’ expressions have been calculated with the help of the compact density matrix method. Our numerical results show that by changing the A, M, and η parameters, we can see a blueshift or redshift in the total optical absorption coefficients (TOACs) and relative refractive index changes (RRICs). Additionally, they are redshifted, and their extrema increase as the radius increases. The increase in electric field or laser field intensities generates a strong displacement of the resonant peak position towards the higher energies, diminishes the TOACs magnitude, and shrinks RRICs extrema. The model potential used in the computation is important, and the study of it will be practical in the development and research of nanostructures systems.
We theoretically investigate the optical absorption coefficient (OAC) in asymmetrical Gaussian potential quantum dots subject to an applied electric field. Confined wave functions together with energies of electron energies in an effective mass approximation framework are obtained. The OAC is expressed according to the iterative method and the compact-density-matrix approach. Based on our results, OAC is sensitively dependent on external electric field together with the incident optical intensity. Additionally, peak shifts into greater energy as the quantum dot radius decrease. Moreover, the parameters of Gaussian potential have a significant influence on the OAC.
Linear and nonlinear optical absorptions in one-dimensional semi-parabolic quantum dot is investigated. The analytical expression of linear and third-order nonlinear optical absorption coefficients are obtained by using compact density-matrix approach and iterative method. Numerical results are presented for an GaAs/AlGaAs quantum dot and the dependence on the quantum confinement of the semi-parabolic quantum dot, the incident optical intensity, and on the relaxation rate are also investigated. The results indicate that the optical absorption coefficients are strongly influenced by the confining frequency, relaxation time, and the incident optical intensity, respectively. However, their influences for the linear optical absorption, third-order nonlinear optical absorption, and the total optical absorption are different. We think our theoretical study may make a great contribution to experimental studies and may open up new opportunities for practical exploitation of the quantum-size effect in optical devices.
The study presents results of the linear and non-linear optical properties of GaAs quantum dots. The reported work aims to provide new results of the quantum dot optical properties confined in Hua plus modified Eckart (HPME) potential. To obtain analytical expressions for the energy eigenvalues and the wave functions, we solved the time-independent Schrödinger equation for the HPME potential by using the parametric Nikiforov-Uvarov (NU) method. Investigation of the linear, third-order nonlinear, and total absorption coefficients and refractive index changes was done with the help of the density matrix approach. The results showed that the energy decreases in a linear manner as the potential parameter, V0. Also, it is observed that as the barrier slope increases, the peaks of the linear, third-order linear, and total absorption coefficient tend to higher values of energy. Furthermore, as the barrier slope increases, the change in refractive indices increases, and their positions shift to higher energies. Additionally, an increase in the structure parameters and optical intensity greatly influences the absorption coefficients and the refractive index changes of the quantum dots.
Simultaneous effects of an on-center hydrogenic impurity and band edge non-parabolicity on intersubband optical absorption coefficients and refractive index changes of a typical GaAs/Al x Ga 1−x As spherical quantum dot are theoretically investigated, using the Luttinger—Kohn effective mass equation. So, electronic structure and optical properties of the system are studied by means of the matrix diagonalization technique and compact density matrix approach, respectively. Finally, effects of an impurity, band edge non-parabolicity, incident light intensity and the dot size on the linear, the third-order nonlinear and the total optical absorption coefficients and refractive index changes are investigated. Our results indicate that, the magnitudes of these optical quantities increase and their peaks shift to higher energies as the influences of the impurity and the band edge non-parabolicity are considered. Moreover, incident light intensity and the dot size have considerable effects on the optical absorption coefficients and refractive index changes.
Abstract This study explores how hydrostatic pressure, temperature, incident light intensity, and structural parameters modulate optical absorption coefficients and refractive index changes in GaAs/Al0.3Ga0.7As spherical quantum dots under the screened cosine Kratzer potential. We use the Nikiforov-Uvarov method to solve the Schrödinger equation to determine the relevant wave functions and energy levels. And using iterative method and density matrix theory, we derived analytical expressions for the optical absorption coefficients and refractive index changes. The results of the numerical analyses demonstrate that both the structural parameters of the quantum dots and the external environmental factors significantly influence the optical absorption coefficients and refractive index changes, with varying degrees of impact. It is particularly noteworthy that these factors are extremely important for modulating the peak amplitude and resonance peak position of the optical absorption coefficients and refractive index changes, providing important theoretical basis for us to deeply understand and modulate the nonlinear optical properties of quantum dots.