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Chinese Physics B

Optical absorption in asymmetrical Gaussian potential quantum dot under the application of an electric field*

Xuechao Li, Chun-Bao Ye, Juan Gao, Bing Wang

Published May 13, 2020• 34 citations
Publisher

Abstract

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.

DOI
10.1088/1674-1056/ab9284

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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.
Abstract In the current work, we have studied the second and third harmonic generation in asymmetrical Gaussian potential quantum dot subjected to the applied electric field. To do this, confined wave function together with energies of electron in an effective mass approximation framework were obtained. Apply these, the analytic expression for the second- and third harmonic generation are determined using a compact density matrix approach and an iterative procedure. According to the results, it is found that applying an electric field, enhances the peak values of the second- and third harmonic generation and redshifts the peak position of their spectrum. Our calculations indicate that increases the radius of quantum dot causes enhances the values of -harmonic generation and redshifts the peak positions of photon energy. It means by optimizing the confinement potential, the maximum –harmonic generation can be obtained. It should be noted that the structural parameters have a significant effect on the –harmonic generation in the considered system.
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.
Electric field influences on the electronic states and the optical absorption in an asymmetrical quantum well with semiparabolic potential are investigated. The formula for the absorption coefficients in this asymmetrical quantum well with electric field are deduced by applying iterative method and density-matrix approach. The results are discussed with GaAs/AlGaAs materials and show that the external electric field has a significant effect on the electronic states and absorption coefficients of asymmetric quantum wells.
Abstract We present a theoretical study on the effects of intense laser field (ILF) and static electric field on the linear and nonlinear optical properties of a cylindrical quantum dot with Rosen–Morse axial potential under the framework of effective mass and parabolic band approximations. This study also takes into account the effects of the structure parameters ( η , V 1 , and R ). The analytical expressions of the linear, third-order nonlinear and total optical absorption coefficients (TOACs) and the relative refractive index changes (RRICs) are obtained by using the compact-density-matrix approach. The results of numerical calculations show that the resonant peak position of the TOACs and RRICs shifts towards lower energies and the magnitude of the peak increases with the effect of the static electric field and ILF. In addition, it is observed that while the resonant energies of the TOACs and RRICs of system shift towards the higher (lower) energies with the enhancement of η , V 1 , they decrease with the augmentation of R . Thus, the findings of this study show that the optical properties of the structure can be adjusted by changing the magnitude of structure parameters and applied external fields.
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.
Abstract In this paper, the effects of external electric, magnetic and non-resonant intense laser fields on the nonlinear optical rectification (NOR), second-harmonic (SH), and third-harmonic (TH) generation in a GaAs quantum well with asymmetrical Gaussian potential are theoretically investigated. Firstly, the energy eigenvalues and eigenfunctions of a single electron confined in the structure are obtained by using the diagonalization method within the framework of the effective-mass and parabolic band approaches. Then, using these energy eigenvalues and eigenfunctions, expressions derived within the compact density matrix approximation has been employed to calculate the coefficients of the nonlinear optical response in the structure. The obtained simulation results show that the influence of the external fields leads to significant changes in the coefficients of nonlinear optical rectification, second and third harmonic generation in the system. As a result, it has been seen that the amplitude and position of the peaks of nonlinear optical rectification, second and third harmonic coefficients can be controlled by changing the applied external fields.