Total Optical Absorption Coefficients Research Articles

Hydrostatic pressure and temperature effects on nonlinear optical properties in harmonic-Gaussian asymmetric double quantum wells

The paper examines the linear and non-linear optical characteristics of an electron in harmonic Gaussian asymmetrical double quantum wells, taking into account thermodynamic variables such as temperature and hydrostatic pressure. Numerical calculations by considering the effective mass and parabolic band approximation are performed. The electron contained within an asymmetric double well generated by the sum of a parabolic and Gaussian potential has its eigenvalues and eigenfunctions determined using the diagonalization approach. For nonlinear optical coefficients, the density matrix expansion is used. Wavefunctions and energy levels vary as an effect of the applied fields. In harmonic Gaussian asymmetrical double quantum wells, the total optical absorption coefficient (TOAC), the relative refractive index changes (RRIC), and second harmonic generation (SHG) have all been theoretically investigated. The magnitude and position of the resonant peaks are significantly influenced by the hydrostatic pressure and temperature effects. With controllable coupling and externally applied hydrostatic pressure and temperature, the potential model presented in this study can be used to simulate and manipulate the optical and electronic properties of the asymmetric double-quantum heterostructures, such as double quantum dots and wells.

Energy spectrum and optical properties in a double parabolic quantum ring: Effects of the impurity, the magnetic field and the spin–orbit interaction

In this letter, the energy spectrum in a concentric double quantum rings(CDQRs) with a parabolic confinement under the influence of the spin–orbit interactions (SOIs), the magnetic field and the hydrogenic donor impurity has been investigated by diagonalizing the Hamiltonian matrix and applying the perturbation theory. Then the optical absorption coefficients (OACs) are calculated through the scheme of compact density-matrix formalism. A discussion of the different intensity of the two SOIs is conducted. Meanwhile, the effects of different factors on the total OACs with different incident light polarization angles have also been investigated, in which the bleaching effects are found.

Optical absorption coefficients of a single electron in a multilayer spherical quantum dot with a Kratzer-like confinement potential

The current study looks at how the Kratzer confinement potential affects the linear, third-order nonlinear, and total optical absorption coefficients (ACs) of a single electron in a multilayered spherical quantum dot (MSQD) by using the finite element method within the effective mass approximation. The variation of the transition energy has been investigated for two allowed transitions, 1p-2s and 2s-2p. Furthermore, we investigated the variation of the linear, third-order nonlinear, and total optical absorption coefficients as a function of the incident photon energy for several transitions while accounting for the effect of the Kratzer confinement potential. The findings show that the optical ACs and transition energy are strongly influenced by the Kratzer confinement potential.

Effect of number of well and core radius on the binding energy and optical properties of multishell spherical quantum dot with parabolic potential

In the current study, the probability densities and binding energy of the ground state and first excited sate in multishell quantum dot with parabolic confinement potential have been examined. Also, the effects of core radius, the number of well in structure and the presence of impurity on the total optical absorption coefficient have been investigated. The finite difference method has been used to obtain the energy levels and related wave functions of the system within framework effective mass approximation. The results obtained reveal that the number of well, especially the first five values, have a considerable impact on the critical core values of binding energy. It is found that the presence of impurity and the number of wells cause a blue shift in the peak positions of total absorption coefficients. Moreover, our results show that these factors have an important effect on the magnitude of optical properties.

Tailoring optoelectronic properties of InGaN-based quantum wells through electric field, indium content, and confinement shape: A theoretical investigation

This paper conducts a comprehensive theoretical examination of the electronic and optical responses, including linear and nonlinear optical responses, of an InGaN-based quantum well with a variable inverted parabolic confinement potential. This examination takes into account the effects of applied vertical electric fields, variable indium content, different confinement shapes, and sizes. The Schrödinger equation is solved numerically using the finite element method and the effective mass theory. The results indicate that both the electrical and optical properties of the system are highly influenced by these factors. Additionally, it is found that by carefully selecting these factors, the total optical absorption coefficient, total refractive index, and linear complex optical susceptibility of the system can be precisely controlled. This study makes a valuable theoretical contribution to the understanding of how electromagnetic radiation interacts with matter and can be applied to help explain the absorption and scattering properties of III-nitride materials, used in the active regions of various devices such as solar cells, photodetectors, and modulators, as well as in the design stages of them.

Investigation on nonlinear optical properties of symmetric and asymmetric double V-shaped AlxGa1-xAs/GaAs potential wells with structural parameters and external electromagnetic fields

ABSTRACT Linear, nonlinear and total optical absorption coefficients and relative refractive index changes for symmetric and asymmetric double V-shaped quantum well configurations formed within AlxGa1-xAs/GaAs heterostructure have been theoretically investigated. Responses of these coefficients to well widths, barrier widths and aluminium concentrations within the barrier as well as applied external electromagnetic fields were the subject of this study. The electronic spectra of the structures are obtained as a solution to the Schrödinger equation with relevant potential and external agents in the framework of effective mass and envelope wave function approximations. The optical properties are calculated by the analytical expressions obtained by iterative solutions within the compact density matrix approach. Although increasing barrier width and aluminium concentration act similarly significant red shifting on the referred coefficients for both symmetric and asymmetric double V-shaped wells, the varying well widths act differently for each configuration. Strengthening electric and magnetic fields shift the resonance peaks to blue for both symmetric and asymmetric wells. The results show that optical properties can be controlled by structural parameters, external probes and asymmetry of double V-shaped wells.

Tuning of nonlinear optical characteristics of a cylindrical quantum dot by external fields and structure parameters

ABSTRACT 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.

Optical Absorption Coefficient and Refractive-Index Change in a Coupled Quantum Dot-Metallic Nanoparticle Structure

In the present work, we investigate the problem of the optical absorption coefficient (OAC) and refractive-index change (RIC) in a semiconductor quantum dot placed in the vicinity of a spherical metallic nanoparticle. We derive the total OAC and RIC from the density-matrix equations through different approaches, one without approximations and the other keeping only linear and third-order nonlinear terms. The derived formulae are then applied in a specific hybrid nanostructure to calculate the OAC and RIC. The results obtained from the derived formulae are used to compare cases of various interparticle distance values and applied light intensities and find that, although for specific distances and intensities the formulae may give similar results, in general, they give different results. Moreover, it becomes clear that the distance between the quantum dot and the metallic nanoparticle, in combination with the polarisation of the light field, plays a significant role in the OAC and RIC of the quantum dot. Expressly, conditional on the polarisation of the applied electric field, the OAC and RIC of the quantum dot can be either enhanced or suppressed close to the metallic nanoparticle compared to their values in the absence of the metallic nanoparticle.

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.

Influence of the intense laser field on optical absorption coefficients and refractive index changes in the double trigonometric quantum wells

In this letter, the effect of the intense laser field on optical properties in the unique double trigonometric quantum wells has been investigated by applying the KH transformation. The Schrdinger equation is solved to obtain the energy levels and the wave functions of this system. Then the optical absorption coefficients (OACs) and refractive index changes (RICs) are calculated through the scheme of the compact density-matrix formalism. The results show that the OACs and RICs undergo a blue-shift first, followed by a red-shift, as the intensity of the laser field is enhanced. Furthermore, features of various transition total OACs are also discussed, which are also affected by the laser field.

Tuning the Nonlinear Optical Properties of Quantum Dot by Noise-Anharmonicity Interaction

Current inspection rigorously explores the tuning of a few relevant nonlinear optical (NLO)properties of GaAs quantum dot (QD) under the stewardship of Gaussian noise-anharmonicity interplay. The NLO properties explored are total optical absorption coefficient (TOAC), total optical refractive index change (TORIC), nonlinear optical rectification (NOR), second harmonic generation (SHG), third harmonic generation (THG), DC-Kerr effect (DCKE), electro-absorption coefficient (EAC), group index (GI)and optical gain (OG). The route of application of noise (additive/multiplicative) to the QD, as well as the symmetry (odd/even) of the anharmonicity, influence the aforesaid NLO properties. These NLO properties exhibit steadfast growth, steadfast fall, maximization, minimization and saturation. The outcomes of the inspection appear to be quite pertinent in the context of the immense technological demand of QD, taking into account the combined impact of anharmonicity and noise.

The effect of structure parameters and static electric field on the nonlinear optical properties of triple InGaAs/GaAs quantum well

Optical properties of InxGa1-xAs/GaAs triple QW are studied for different quantum well thicknesses and external electric fields. The effective mass approximation is used to calculate the band alignment of the structure. The finite difference method (FDM) is applied to solve the 1D- Schrödinger equation. Intersubband energies and the total optical absorption coefficients (TOACs) and total relative refractive index changes (RRICs) are numerically calculated under the applied external electric field. The structure parameters and applied electric field cause the separation of the energy levels and variation of the dipole moment matrix elements. These separations are responsible for the resonant peak shifts. It is shown that the varied structure parameters and external electric field cause red or blue shifts in the resonant peak position of TOAC and RRIC coefficients.

Investigation of linear and nonlinear optical absorption coefficients and refractive index changes of a zigzag quantum well with structure parameters and applied external fields

In this study, we have investigated some linear and nonlinear optical properties of GaAs/GaAlAs zigzag quantum well structures under different electric and magnetic field intensities. We also examined the effect of adjustable structural parameters as well as width on the optical response of the system. The diagonalization method has been the tool to numerically solve the effective mass approximation Schrödinger equation obtaining the energy levels and related wave functions needed to evaluate the expressions of linear, third-order nonlinear, and total optical absorption coefficients and relative refractive index changes derived within the compact density matrix method. Results show that the optical response becomes blue-shifted with the applied electric and magnetic fields’ increment.

Spectral features and optical absorption of vertically stacked V-groove quantum wires

The spectral features and the linear, nonlinear, and total optical absorption coefficients of two realistic mathrm {GaAs/Ga}_{1-x}{mathrm{Al}}_x{mathrm{As}} vertically stacked V-groove quantum wires confining electronic states were theoretically studied. The compact density matrix formalism and the finite element method were used as solution frameworks. The influence of the barrier width, inter-sidewall angle, the crescent thickness of the stack, and the influence of a static electric field on the energy spectrum and the optical coefficients is addressed. Increasing the crescent thickness (inter-sidewall angle) leads to a reduction (non-monotonous increase) of the energy values, while the presence of a static electric field leads to controllable stark-like patterns. In all cases, anti-crossing points are reported. By increasing the crescent thickness, inter-sidewall angle, or barrier width, a non-monotonous blue-/red-shift of the resonant peaks of the optical absorption is observed. In addition, the results in asymmetric/symmetric vertically coupled V-groove quantum wire systems suggest that the quantum tunneling phenomenon can be linked to the enhancement of the total optical absorption due to the possibility of the generation of dipole moments by higher electron mobility. Thus, optical fields oriented along the growth direction enhance the optical absorption. Furthermore, the absorption coefficient maximum is drastically modified by varying the inter-sidewall angle, and even the evolution tendency can be inverted due to the anti-crossing points in the energy spectra. Since the obtained resonant peaks are located below 20 meV in the spectra, the analyzed system could be interesting for exploring and designing new Terahertz devices.

The nonlinear optical properties of GaAs/GaAlAs triple quantum well: Role of the electromagnetic fields and structural parameters

Being relevant to the field of device applications, multiple semiconductor quantum wells are systems that exhibit remarkable optical and electronic properties. These can be properly tuned by suitably modifying the composition, structural parameters, and the application of external probes. Here, the electronic and optical properties of a GaAs/GaAlAs triple quantum well have been investigated under the influence of applied electric and magnetic fields, as well as the change of well and barrier widths. We have used the diagonalization method to numerically solve the Schrödinger equation under the effective mass approximation for obtaining the subband energy levels and related electronic wave functions. The expressions used for evaluating linear, third-order nonlinear, and total optical absorption coefficients (TOACs) and relative refractive index changes (RRICs) were previously derived within the compact density matrix method. According to our results, whilst an increment in the applied electric field causes a red shift in TOACs and RRICs, a blue shift of the optical responses occurs with increasing the applied magnetic field. Besides, a blue shift is observed as well by changing the width of the central well (LwL), whilst a red shift is noticed when changing left and right wells (LwL and LwR) and barrier (LbL and LbR) widths for zero fields. We believe that our study could make a contribution to designing new quantum-well-based optoelectronic devices.

Effects of hydrostatic pressure and temperature on the nonlinear optical properties of GaAs/GaAlAs zigzag quantum well

ABSTRACT We have examined theoretically how the temperature and the hydrostatic pressure affect the total optical absorption coefficients, the total refractive index changes, and the second harmonic generation coefficients for GaAs/GaAlAs zigzag quantum well structure. The diagonalisation method and the effective mass approximation have been used to obtain the numerical solution of the Schrödinger equation and energy levels, respectively. The analytical expressions of the optical properties were obtained by using the compact density matrix and iterative methods. When the temperature (hydrostatic pressure) is increased, the resonant peaks’ positions of the total optical absorption coefficients and the relative refractive index changes are shifted to higher energies/blueshift (lower energies/red-shift) with amplitude increment (decrement). Additionally, the resonant peak position of the second harmonic generation coefficient shifts to higher energies/blueshift (lower energies) and also decrease (increase) in magnitude with increasing temperature (hydrostatic pressure).

Effects of Applied Magnetic Field on the Optical Properties and Binding Energies Spherical GaAs Quantum Dot with Donor Impurity.

The screened modified Kratzer potential (SMKP) model is utilized to scrutinize the impacts of an applied magnetic field (MF) on the binding energies and linear and nonlinear optical properties spherical GaAs quantum dot with donor impurity (DI). To accomplish this goal, we have used the diagonalization method to numerically solve the Schrödinger equation under the effective mass approximation for obtaining the electron energy levels and related electronic wave functions. The expressions used for evaluating linear, third-order nonlinear, and total optical absorption coefficients and relative refractive index changes were previously derived within the compact density matrix method. It has been shown here that the MF and DI impacts the characteristics of the absorption coefficients and the refractive index changes. This study’s results will find application in optoelectronics and related areas.

The impact of hydrostatic pressure and temperature on the binding energy, linear, third-order nonlinear, and total optical absorption coefficients and refractive index changes of a hydrogenic donor impurity confined in GaAs/AlxGa1−xAs double quantum dots

The impact of hydrostatic pressure and temperature on the binding energy, linear, third-order nonlinear, and total optical absorption coefficients and refractive index changes of a hydrogenic donor impurity confined in GaAs/AlxGa1−xAs double quantum dots

Optical absorption in core-shell quantum antidot under applied co-directed electric and magnetic fields

Using the matrix diagonalization method within the effective mass approximation and the rectangular potential profile, we investigate optical absorption coefficients (OAC) in the core-shell quantum antidot (QAD) Al0.3Ga0.7 As/GaAs/Al0.3Ga0.7 As in the presence of applied co-directed electrical and magnetic fields. The electric field effect on the electron wave functions, energy spectrum, oscillator strength of the intersubband electronic transitions is calculated for different size of QAD core and different value of the magnetic field induction. The total, linear and nonlinear optical absorption coefficients in QAD are obtained by considering 1 s-1p and 1p-1d electron quantum transitions as functions of the incident photon energy.

Effects of magnetic, electric, and intense laser fields on the optical properties of AlGaAs/GaAs quantum wells for terahertz photodetectors

We investigate optical absorption coefficients and changes in the refractive index in single- and double-step GaAs/AlGaAs quantum wells under the influence of magnetic, electric, and intense laser fields. For single-step quantum wells, increasing the intensity of the external laser and electric fields induces a red-shift in the total optical absorption coefficient and change in the refractive index and increases their amplitudes; however, increasing the magnetic field generates a blueshift in the optical absorption and change in the refractive index. For double-step quantum wells, the transition energy between the ground and first excited state is strongly decreased. In addition, the total optical absorption coefficients and changes in the refractive index incur a blue shift when the electric and magnetic fields are increased and a red-shift with increasing laser fields. Our analysis of coupling matrix elements, probability densities, and energy levels show that intense laser, electric, and magnetic fields can be harnessed to adjust and tune total optical absorption coefficients and refractive indices for terahertz applications.