Properties Of Spherical Quantum Dot Research Articles

Optical properties of spherical quantum dot using screened Kratzer potential

Here we investigate the optical properties of a spherical quantum dot using the screened Kratzer potential. The density matrix formalism is employed to study refractive index changes, along with linear and nonlinear optical absorption coefficients. To this effect, the radial Schrödinger equation is solved using the Nikiforov–Uvarov functional analysis method, resulting in analytical expressions for the energy eigenvalues and the associated eigen functions. Effects of dot size, potential parameters, and screening length on these properties are analyzed in detail for a GaAs quantum dot. The obtained results reveal that the optical response of the system is highly sensitive to the dot size and potential parameters, and thus it can be tuned accordingly. The impact of external magnetic and Aharonov–Bohm flux fields on the optical properties of the GaAs quantum dot is also discussed. The findings of this study may provide useful insights in design and optimization of quantum dot-based optoelectronic devices.

Nonlinear optical properties in GaAs/Ga0.7Al0.3As spherical quantum dots with Like-Deng-Fan-Eckart potential

The effects of several key factors on the nonlinear optical properties of spherical quantum dots (QDs) with like-Deng-Fan-Eckart potential are studied theoretically, aiming at nonlinear optical absorption coefficients (OACs) and refractive index changes (RICs). By using the Factorization method to solve the Schrödinger equation, the dependent wave functions and energy levels are determined, and the analytical expressions of OACs and RICs are obtained by making use of the iterative method and density-matrix theory. It is worth noting that the numerical results show that the radius of QDs, the depth of limiting potential and the tuned effective mass have an enormous impact on the peaks and formants of OACs and RICs.

Effects of the confinement potential parameters and optical intensity on the linear and nonlinear optical properties of spherical quantum dots

We study the linear and nonlinear optical properties of a spherical GaAs quantum dot with screened modified Kratzer potential (SMKP) by solving the time-independent Schrödinger wave equation using the diagonalization method. The obtained electronic properties of the system alongside the compact density formalism are used to evaluate the linear, third-order nonlinear and total optical absorption coefficients and change in the relative refractive index of the system. We show that the confinement potential parameters and optical intensity significantly affects the behaviour of absorption coefficients and refractive index changes. It is important to note that the findings of this study will find application in optoelectronics and related areas.

Impact of Applied Temperature and Hydrostatic Pressure on the Off-Center Donor Spectrum in Spherical Quantum Dot

Within the effective mass approximation and the infinite confinement potential, this work focused on studying the electronic properties of spherical quantum dot (SQD) nanostructure through the finite difference method. The effects of shallow donor impurity position, temperature (T), and hydrostatic pressure (P) on the binding energy, the electron spatial extension <re> and the average electron-impurity distance <rD-e> in a SQD have been evaluated. Our findings show that the binding energy increases as a function of hydrostatic pressure and decreases with the temperature effect. However, the binding energy presents very clear maximum around the spherical nanostructure center depending on the impurity position. For higher SQD, the impact of externals perturbations (P and T) on the electron spatial extension are more significant. The distance <re> decreases with the augmentation of hydrostatic pressure when the impurity is near the center, which is conversely when the impurity is near the edge. In addition, applying the hydrostatic pressure and temperature leads to decreasing and increasing the average distance <rD-e>, respectively.

Calculation of linear and nonlinear optical properties of spherical quantum dots with Hulthén plus Hellmann confining potential

The optical absorption coefficients (OACs) and refractive index changes (RICs) in the GaAs/Ga1−x AlxAs spherical quantum dots (QDs) under Hulthén plus Hellmann confining potential have been investigated by adjusting the structural parameters with the applied tuning elements. Energy levels and wavefunctions of this system have been determined by means of the Nikiforov–Uvarov (NU) method. Expressions for the OACs and RICs are derived by the density matrix method. We display that both the radius of QDs and the depth of the Hulthén plus Hellmann confining potential have a significant impact on OACs and RICs. Furthermore, we can draw conclusions that the applied tuning elements can manage the amplitudes and resonances frequency of the OACs and RICs.

Optical properties of spherical quantum dot in the presence of donor impurity under the magnetic field

In this study, the binding energies of an on-center and off-center hydrogenic donor impurity in a spherical quantum dot with finite confinement potential under an applied external magnetic field are investigated in detail by using the matrix diagonalization method in the effective mass approximation. Depending on the calculated energies and wave functions, the linear, third-order nonlinear and total optical absorption coefficients between the ground and several excited states are examined by the iterative method in the compact density matrix approximation for the two-level system. The combined effect of donor position, magnetic field and dot size on binding energies and optical absorption coefficients is observed. The results show that these effects cause significant changes on donor binding energy and optical absorption coefficients.

Effect of magnetic field on energy states and optical properties of quantum dots and quantum antidots

In this study, the effect of magnetic field on electronic spectra and optical properties of spherical quantum dot (QD) and quantum anti-dot (QAD) are investigated. The energies and corresponding wave functions are calculated by using the finite difference method and oscillator strengths are obtained based on the dipole approximation approach. Based on perturbation theory, our theoretical results are presented and it will be shown clearly how the magnetic field affects energy levels and intersubband transitions. In the following, our numerical results based on a comparative perspective for both QD and QAD models are given. Our results indicate that in the presence of magnetic field, changes on energy levels and optical properties of QD and QAD are considerably different. In addition, we study the effect of change in core and shell dimensions in the presence of magnetic field on the energy states and oscillator strengths of both nanostructures.

Hydrogenic impurity effect on the optical nonlinear absorption properties of spherical quantum dots with a parabolic potential

The linear, third-order and total optical absorption coefficients of a hydrogenic impurity in spherical quantum dots subjected to a parabolic potential are calculated by the compact density-matrix approach and the finite difference method. The effect of the potential parameter $\gamma_{p}$ and the confining radius R on the optical absorption coefficients of the spherical quantum dots are investigated. The following conclusions are drawn: 1) The reduction of the size of the quantum dot can lead to a blue-shift of the absorption spectrum no matter whether there is an impurity or not; however, the intensity of the absorption spectrum slightly decreases as an impurity is introduced into the spherical quantum dot. 2) The saturation case of total optical absorption coefficients is observed more easily in the case of weak confinement than in the case of strong confinement; and there is a one-to-one correspondence relationship among the intensity of the absorption peak, the potential parameter $\gamma_{p}$ and the saturation intensity Is, corresponding to the saturation case of the total optical absorption coefficients. 3) There is an approximate linear relationship between the value of Is and the value of $ \gamma_{p}$ as the value of $ \gamma_{p}$ is large.

Polaron and dielectric mismatch effects on impurity-related optical absorption and refractive index changes in a spherical quantum dot

The influence of both dielectric mismatch and electron-phonon interaction (EPI) effects on the linear and nonlinear optical properties of spherical quantum dots (QDs) with a shallow hydrogenic impurity under electric field are studied. The interplay among confinement geometry, dielectric mismatch, electron-phonon interaction, and the Stark effect on the oscillator strengths, absorption coefficients (ACs) and refractive index changes (RICs) has been revealed. The results show that the polaron effect and/or image charges lead to the blue shifts of absorption coefficients and refractive index changes. As a result of a quantum confinement Stark effect the red shifts of optical characteristics with increasing electric field have been observed. This indicates that the impurity-related optical characteristics of quantum dots can be controlled by the Stark confinement.

Effects of Temperature, Pressure, and Size on Different Transitions of Optical Properties of Spherical Quantum Dot

In this paper, the effects of temperature, pressure, and size on the maximum of optical absorption coefficients and refractive index changes of GaAs quantum dots with a hydrogen impurity for different electronic transitions are calculated. For this propose, the effects of temperature, pressure, and size on the bandgap energy, the effective mass, and the dielectric constant are studied. Using Runge–Kutta numerical method, the eigenenergies and the eigenstates are calculated. Results show that increasing the pressure (temperature) shifts the optical properties to high photon energy and leads to decreasing (increasing) of its peak, while increasing the size shifts it to low photon energy and fluctuates its peak. Also, the s–p transition occurs in lower photon energy than the other transitions. Additionally, one can see stability behavior in fluctuations of temperature for the optical properties of s–p transition compare to the other transition. Finally, the maximum value of optical properties for different transition is fluctuated by changing the size.

Linear and nonlinear optical properties in spherical quantum dots: Manning-Rosen potential

In this work, we studied the optical properties of spherical quantum dots confined in Manning-Rosen potential with the appropriate centrifugal term included. The approximate solution of the bound state and wave functions were obtained from the Schrodinger wave equation by applying the standard methods. Also, we have used the density matrix formalism to investigate the linear and third-order nonlinear absorption coefficient and refractive index changes.

Linear and Nonlinear Optical Properties in Spherical Quantum Dots: Generalized Hulthén Potential

In this work, we studied the optical properties of spherical quantum dots confined in Hulthen potential with the appropriate centrifugal term included. The approximate solution of the bound state and wave functions were obtained from the Schrodinger wave equation by applying the factorization method. Also, we have used the density matrix formalism to investigate the linear and third-order nonlinear absorption coefficient and refractive index changes.

Optical properties of spherical quantum dot with on-center hydrogen impurity in magnetic field

This paper studies linear and nonlinear optical properties of the GaAs spherical quantum dot (QD) with impenetrable walls, containing on-center hydrogen impurity, under the presence of the static magnetic field. Transition energy and electric dipole transition matrix element between the impurity electron ground and the first excited state with \(m = 0\) have been computed using the Lagrange mesh method within the effective mass approximation. The linear and the third-order nonlinear optical absorption coefficients (ACs) are obtained using the iterative procedure in the framework of the density matrix approach, and their behavior with respect to the incident photon energy is discussed. In addition, the dependence of these coefficients on the QD radius, magnetic field strength, intensity of the applied laser field and relaxation time is studied. It has been found that for large values of relaxation time, the nonlinear AC prevails over the linear one and the total AC becomes negative.

Spontaneous emission control of quantum dots embedded in photonic crystals: Effects of external fields and dimension

In this paper simultaneous effects of external electric and magnetic fields and quantum confinement on the radiation properties of spherical quantum dot embedded in a photonic crystal are investigated. Under the influence of photonic band-gap, effects of external static fields and dot dimension on the amplitude and spectrum of different radiation fields emitted by the quantum dot are studied. Our results show the considerable effects of external fields and quantum confinement on the spontaneous emission of the system.

Application of Tietz potential to study optical properties of spherical quantum dots

In this work, we study the optical properties of spherical quantum dots by using Tietz potential. In this regard, we have applied Nikiforov–Uvarov (NU) technique and numerically solved the Schrodinger equation to obtain energy levels and wave functions. Then, by using the density matrix method, we have derived expressions for the changes in linear and third-order nonlinear absorption coefficients and refractive index. According to the results obtained from this work, it is deduced that: (i) the total refractive index and the absorption coefficients increase and shift towards higher energies as v0 increases; (ii) the total absorption coefficient and refractive index decrease and also shift towards lower energies as r0 increases.

Polaronic effect on linear and nonlinear optical properties of spherical quantum dots under electric field

The polaronic effect on the linear and nonlinear optical properties of spherical quantum dots with a shallow hydrogenic impurity under electric field are studied, taking into account the interactions with both confined and surface optical phonons. In addition, the interaction between impurity and phonons has also been considered. Numerical results on typical Zn1−xCdxSe/ZnSe material show that the polaronic effect or electric field redshifts the peak positions of linear and nonlinear optical absorption coefficients and refractive index changes, but does not significantly affect the peak values of them. The polaronic effect is enhanced with the decreasing quantum dot radius or Zn concentrations. Additionally, it is found that the electric field has an important influence on the polaronic effect especially on the surface optical phonons.

Linear and nonlinear optical properties in spherical quantum dots: Rosen-Morse potential

In this paper, we have studied optical properties of spherical quantum dots by using Rosen-Morse potential. In this regard, we have first solved the Schrodinger equation and obtained energy levels and wave functions by applying Nikiforov-Uvarov (NU) method. Then, by using density matrix method, we have applied analytical expressions for the linear and third-order nonlinear absorption coefficient and refractive index changes. The results show that the total refractive index changes and the absorption coefficients increase and shift towards higher by enhancing height potential.

Optical properties of spherical quantum dot with modified Pöschl–Teller potential

In this paper the electronic and hole states in three regimes of size quantization in spherical quantum dot with modified Pöschl–Teller potential made of GaAs are studied. Energy spectrum is compared with the parabolic approximation case for the regime of strong size quantization. Analytical expressions for the particle energy spectrum, absorption coefficient and dependencies of effective threshold frequencies of absorption on the radius of quantum dot are obtained for strong and weak size quantization regimes. The problem solved in the framework of variation method for the intermediate size quantization regime. The selection rules corresponding to different transitions between quantum levels are found. The size dispersion distribution of growing quantum dots by the radius have been taken into account by three experimentally realizing distribution functions. Distribution functions of Gaussian, Lifshits–Slezov and Gamma have been considered.

Optical properties of spherical quantum dot with position-dependent effective mass

In this paper, the effects of position-dependent effective mass on the optical properties of a three dimensional quantum dot are numerically investigated. For this purpose, by using the point canonical transformation method and numerical solution of the Schrödinger equation, the energy levels and wave functions of electrons in the confinement potential are obtained. Then the optical properties are studied by considering the compact density matrix approach based on the numerical calculation of the wave function. Our calculations were compared with the case of constant mass. Results show that the position-dependent effective mass plays an important role in the intersubband optical absorption coefficient and refractive index changes in a quantum dot.

Spin–orbit interaction effects on the optical properties of spherical quantum dot

In this paper simultaneous effects of Rashba spin–orbit interaction and quantum confinement on the optical absorption coefficient and refractive index of a typical spherical GaAs quantum dot are studied. Based on the results obtained in our recent paper [B. Vaseghi, et. al., Phys. Lett. A 375 (2011) 2747] it is shown that, absorption coefficient increases and refractive index changes remain constant with considering the SOI. Moreover, the spectrum of these optical quantities move toward higher energies of incident photons as SOI strength increases. The interesting point is that, the SOI effect varies with dimension and depends on the quantum confinement.