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理论物理通讯:英文版

Absorption Spectra and Refractive Index Changes of an Exciton in a Core/Shell Quantum Dot

Xie Wen

Published Jan 1, 2015• 0 citations
OpenAlex

Abstract

The absorption spectra and the refractive index changes are calculated theoretically for an exciton in a core/shell quantum dot. The advantage of our methodology is that one can investigate the influence of the repulsive core by varying two parameters in the confinement potential. The dimensionality effect of exciton quantum dots on the optical absorptions has been studied. It has been found that in the same regime, the optical absorption intensities of excitons are much smaller for the core/shell quantum dots than for the two-dimensional quantum rings. The linear and the nonlinear optical absorption coefficients and refractive index changes have been examined with the change of the confinement potential. The results show that the optical absorptions and the refractive index changes are strongly affected by the repulsive core of core/shell quantum dots. Moreover, the calculated results also reveal that as the inner radius increases, the peak values of the absorption coefficients and the refractive index changes of an exciton will show the optical Aharonov–Bohm oscillation in core/shell quantum dots.

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Absorption Spectra and Refractive Index Changes of an Exciton in a Core/Shell Quantum Dot

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Abstract The absorption spectra and the refractive index changes are calculated theoretically for an exciton in a core/shell quantum dot. The advantage of our methodology is that one can investigate the influence of the repulsive core by varying two parameters in the confinement potential. The dimensionality effect of exciton quantum dots on the optical absorptions has been studied. It has been found that in the same regime, the optical absorption intensities of excitons are much smaller for the core/shell quantum dots than for the two-dimensional quantum rings. The linear and the nonlinear optical absorption coefficients and refractive index changes have been examined with the change of the confinement potential. The results show that the optical absorptions and the refractive index changes are strongly affected by the repulsive core of core/shell quantum dots. Moreover, the calculated results also reveal that as the inner radius increases, the peak values of the absorption coefficients and the refractive index changes of an exciton will show the optical Aharonov-Bohm oscillation in core/shell quantum dots.

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The absorption spectra and the refractive index changes are calculated theoretically for an exciton in a core/shell quantum dot. The advantage of our methodology is that one can investigate the influence of the repulsive core by varying two parameters in the confinement potential. The dimensionality effect of exciton quantum dots on the optical absorptions has been studied. It has been found that in the same regime, the optical absorption intensities of excitons are much smaller for the core/shell quantum dots than for the two-dimensional quantum rings. The linear and the nonlinear optical absorption coefficients and refractive index changes have been examined with the change of the confinement potential. The results show that the optical absorptions and the refractive index changes are strongly affected by the repulsive core of core/shell quantum dots. Moreover, the calculated results also reveal that as the inner radius increases, the peak values of the absorption coefficients and the refractive index changes of an exciton will show the optical Aharonov–Bohm oscillation in core/shell quantum dots.
Abstract The absorption spectra and the refractive index changes are calculated theoretically for an exciton in a core/shell quantum dot. The advantage of our methodology is that one can investigate the influence of the repulsive core by varying two parameters in the confinement potential. The dimensionality effect of exciton quantum dots on the optical absorptions has been studied. It has been found that in the same regime, the optical absorption intensities of excitons are much smaller for the core/shell quantum dots than for the two-dimensional quantum rings. The linear and the nonlinear optical absorption coefficients and refractive index changes have been examined with the change of the confinement potential. The results show that the optical absorptions and the refractive index changes are strongly affected by the repulsive core of core/shell quantum dots. Moreover, the calculated results also reveal that as the inner radius increases, the peak values of the absorption coefficients and the refractive index changes of an exciton will show the optical Aharonov-Bohm oscillation in core/shell quantum dots.
We study the optical absorptions of an exciton in a quantum ring. The quantum ring is described as a circular quantum dot with a repulsive core. The advantage of our methodology is that one can investigate the influence of the repulsive core by varying two parameters in the confinement potential. The linear, third-order nonlinear and total optical absorption coefficients have been examined with the change of the confinement potential. The results show that the optical absorptions are strongly affected by the repulsive core. Moreover, the repulsive core can influence the oscillation in the resonant peak of the absorption coefficients.
Analytical expressions of the optical absorption coefficients and refractive index changes in a two-electron quantum dot with oscillating and linear confining terms are obtained by using compact-density matrix approach and exact analytical method. Numerical results on typical GaAs/AlGaAs materials show that, an increase of the confinements blueshifts the peak positions of absorption coefficients and refractive index changes. Additionally, an increase of the optical intensity and relaxation time considerably changes the absorption coefficients as well as the refractive index changes.
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.
In the current study, linear, nonlinear and total relative refractive index changes of a single shallow hydrogenic donor atom confined in semiconductor core/shell/shell quantum dot heterostructure are investigated in detail by compact density matrix formalism. For this purpose, the energy eigenvalues and the corresponding wave functions are calculated by diagonalization method in the effective mass approximation. Then, intersubband 1s→1p and 1p→1d donor transition energies are calculated. In the study, the effects of core/shell sizes, donor position and depth of confinement potential are analyzed. The numerical results show that the linear and nonlinear refractive index changes undergo significant changes.
The linear and the third-order nonlinear optical properties of an exciton confined in a three-dimensional quantum dot with a parabolic potential are studied in a static magnetic field. Eigenvalues, wave functions, dipole matrix elements and selection rules are calculated analytically. Based on the calculated energies and wave functions, within the effective mass approximation, a compact-density matrix approach is employed to analyse the absorption coefficients and refractive index changes. The study is first of its kind since the excitonic effects are studied in a static magnetic field considering both the confinement potential and the electrostatic interaction between the electron-hole pair. An important finding of our research is the dependence of the magnitude of absorption coefficients on the radius of the quantum dot, the result that may have broad implications in future device designing.