Electronic states and nonlinear optical properties of a two‐dimensional hexagonal quantum dot: Effects of impurity, geometrical size and confinement potential
Abstract:Phone: þ98 741 222 3048, Fax: þ98 741 222 3048In the present work, the linear and the third-order nonlinear optical absorption coefficients as well as refractive-index changes in a two-dimensional hexagonal quantum dot with the presence of an impurity are calculated. A matrix diagonalization method is used to calculate energy levels and corresponding wave functions in the effective-mass approximation. Also, by means of the compact-density matrix approach the linear and nonlinear optical absorption coefficients… Show more
“…Thus, the impurity driven modulation of linear and nonlinear optical properties has persistently gained importance because of emerging applications in photodetectors and high‐speed electro‐optical devices (). Naturally, a good number of theoretical and experimental works have been conducted on both linear and nonlinear optical properties of these structures .…”
We investigate the profiles of diagonal components of static and frequency‐dependent third nonlinear (γxxxx, γyyyy) polarizability of repulsive impurity doped quantum dots driven by noise. The dopant impurity potential is represented by a Gaussian function. We have invoked Gaussian white noise applied additively and multiplicatively (in Stratonovich sense). In order to determine the polarizability components, the doped system is subject to an external electric field of given intensity, which may be static or time‐dependent. The dopant location and the noise characteristics delicately tailor the polarizability components and produce good number of interesting outcomes. Quiet significantly, we have found ineffectiveness of the noise strength in influencing the polarizability components when the noise is applied additively. However, the multiplicative noise behaves otherwise and gives rise to additional interesting features in the polarizability profiles. The multiplicative noise even causes noticeable enhancement in the magnitude of the polarizability components. The present enquiry gains importance in view of the fact that noise seriously affects the optical properties of doped quantum dot devices. The findings could be relevant within the purview of noise driven optical properties of doped quantum dot systems.
“…Thus, the impurity driven modulation of linear and nonlinear optical properties has persistently gained importance because of emerging applications in photodetectors and high‐speed electro‐optical devices (). Naturally, a good number of theoretical and experimental works have been conducted on both linear and nonlinear optical properties of these structures .…”
We investigate the profiles of diagonal components of static and frequency‐dependent third nonlinear (γxxxx, γyyyy) polarizability of repulsive impurity doped quantum dots driven by noise. The dopant impurity potential is represented by a Gaussian function. We have invoked Gaussian white noise applied additively and multiplicatively (in Stratonovich sense). In order to determine the polarizability components, the doped system is subject to an external electric field of given intensity, which may be static or time‐dependent. The dopant location and the noise characteristics delicately tailor the polarizability components and produce good number of interesting outcomes. Quiet significantly, we have found ineffectiveness of the noise strength in influencing the polarizability components when the noise is applied additively. However, the multiplicative noise behaves otherwise and gives rise to additional interesting features in the polarizability profiles. The multiplicative noise even causes noticeable enhancement in the magnitude of the polarizability components. The present enquiry gains importance in view of the fact that noise seriously affects the optical properties of doped quantum dot devices. The findings could be relevant within the purview of noise driven optical properties of doped quantum dot systems.
“…Nowadays, with the advances in nanofabrication technologies like R. Khordad & H. Bahramiyan epitaxial techniques and metal-organic chemical vapor deposition, [6][7][8] it is possible for researchers to fabricate quantum wire structures of nanometer size with various cross-sections such as triangular, parallelogram, V-shape, T-shape, square, circular and hexagonal. [9][10][11][12] For example, Tsetseri et al 13 calculated the low-temperature electron mobility in V-shaped quantum well wires. Mohan et al 14 investigated the spectrum of luminescent hexagon superlattice, created by InP/InAs/InP nanotubes with the transversal cross-section of right hexagon shape.…”
In this paper, we have studied the effect of impurity on the energy levels and nonlinear optical properties of a hexagon-shaped quantum wire using finite element method (FEM). We have obtained the energy eigenvalues, their corresponding eigenfunctions and third harmonic generation (THG) with and without impurity for different sizes of inner a 1 and outer a 2 hexagons. It is found that all energy levels are decreased with increasing a 1 . There is degeneracy between energy levels without impurity. But, there is no degeneracy between the energy levels in the presence of impurity. The dipole matrix elements are increased with enhancing hexagon sizes without impurity. But, these elements have complex behaviors with impurity. The THG increases and shifts toward lower energies by enhancing a 1 . The influence of a 2 /a 1 on THG is not large when a 2 /a 1 > 2. The THG shifts toward lower energies by increasing impurity position.
“…S M Azami et al studied the energy levels, the nonlinear OACs, and refractive index changes in a two-dimensional hexagonal QD [13]. G. Rezaei et al calculated the influence of a center hydrogenic impurity on the nonlinear refractive index changes and OACs in a two-dimensional hexagonal QD [14]. The numerical results above showed that the size of the QD, confined potential, hydrogenic impurity, and external fields play an essential role in the nonlinear optical properties.…”
In this paper, the energy levels and nonlinear optical properties modulated by the applied electric field are analytically investigated where a hydrogenic impurity is confined in the GaAs/GaAlAs hexagonal quantum dot(QD). The linear and nonlinear optical absorption coefficients(OACs) have been obtained by using the compact density matrix and iterative approach. In the one electron approximation, an off-center hydrogenic donor impurity is considered, and the results show that the energy levels and nonlinear optical absorption of the dot depend strongly on the hydrogenic impurity. Especially, The overall results show that the geometric parameter and the magnitude of confinement potential of hexagonal QD, and the applied electric field act a very important role in the electronic and optical properties of hexagonal QD.
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