Total Refractive Index Changes Research Articles

Optical and electronic properties of a two-dimensional quantum ring under rotating effects

This work presents a theoretical study on the effects of rotation on the nonrelativistic quantum motion of a charged particle confined to a 2D ring in the presence of the Aharonov–Bohm effect and a uniform magnetic field. We formulate the Schrödinger equation with minimal coupling, incorporating the gauge field for the rotating frame and the potential vector of the electromagnetic field. By solving the equation of motion, we determine the eigenvalues and eigenfunctions of the particle. We analyze the probability distribution as a function of varying rotating parameter values and observe a perceptible shift in the distribution. This shift indicates a higher probability of locating the electron at the edges of the ring. The second part of our study focuses on the investigation of rotation effects on the linear and nonlinear optical properties of the system. Specifically, we examine the linear, nonlinear, and total refractive index changes, as well as the optical absorption coefficients. Through numerical analysis, we demonstrate significant rotating effects on energy levels and optical properties. Our findings indicate that, for the considered physical parameters, the impact of rotation on the optical properties becomes prominent at values on the order of a few terahertz.

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 properties of a single quantum well with Pöschl–Teller confinement potential

In this work, using the compact density matrix approach and iterative procedure, the effects of the two asymmetry parameters of the Pöschl-Teller quantum well (QW) on the nonlinear optical rectification (NOR), second harmonic generation (SHG), third harmonic generation (THG), inter-subband optical absorption coefficient (IOAC), and refractive index change (RIC) are studied. Numerical results reveal that the two asymmetry parameters ν and μ of the Pöschl-Teller QW have a great influence on the NOR, SHG, THG, IOACs, and RICs. The maximum asymmetry of the Pöschl-Teller confinement potential can be gotten by an optimized set of two ν and μ asymmetry parameters. If it is desired to obtain the NOR, SHG, THG, and total RIC (IOAC) with larger values, then a relatively small (large) value of μ / ν should be employed. Significant high-order nonlinear can be obtained via a correct choice of the set of the two asymmetry parameters. The results of our study show that the Pöschl-Teller QW is a promising candidate for optoelectronic device applications. • The asymmetry parameters ( ν and μ ) of the Pöschl-Teller QW have great influences on the NOR, SHG, THG, ACs, and RICs. • The maximum asymmetry of the Pöschl-Teller confinement potential can be gotten by an optimized set of ν and μ . • If it is desired to obtain the NOR, SHG, THG, and total RIC (IOAC) with larger values, then a relatively small (large) value of ν and μ should be employed. • Significant high-order nonlinear can be obtained via a correct choice of the set of ν and μ . • The results of our study show that the Pöschl-Teller QW is a promising candidate for optoelectronic device applications.

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 total absorption coefficient and refractive index change of a spherical quantum dot in the confinement radial potential

We have systematically investigated the linear, third-order nonlinear, total absorption coefficients and refractive index change of the spherical quantum dot in the confinement potential family V(r)=Ar2−Br+Crκ by solving the radial Schrödinger equation with the Numerov method in case of the effective mass approximation for the allowed transition of the ground state (1s) to first excited state (2p). We examine the dependencies of the total absorption coefficient and refractive index change on the confinement potential parameters for varying incident photon energy and relaxation times. Our results demonstrate that the absorption coefficients and the change in refractive index strongly depend on the confining potential parameters non-linearly representing various intersubband transitions of quantum dots. We find that increasing the parameter B in the Coulomb plus harmonic oscillator potential or decreasing the parameter A in the Kratzer plus harmonic oscillator potential, the total absorption coefficient and refractive index change shift to higher photon energies.

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.

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.

Linear and nonlinear optical properties in spherical quantum dots: Modified Möbius squared potential

The optical properties of quantum dots (QDs) in modified Möbius squared (MMS) potential are studied. To obtain the energy expressions and the wave functions, we solved the Schrödinger equation by using Nikiforov-Uvarov (NU) method. We investigated the linear, third-order nonlinear and total absorption coefficients (AC) and refractive index changes (RIC) using the density matrix. The numerical results show that the structure parameters and optical intensity have a strong influence on AC and RIC.

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

Charge-current generations and optical specifications of Gaussian quantum dot with energy-dependent potential

We consider the energy-dependent quantum dot with GaAs/GaAlAs Gaussian potential encompassment. Depending on the experimental or theoretical results for different types of interactions, the energy dependency can also be chosen as quadratic, fractional or any other type. The solutions of the wave equation for the energy-dependent Gaussian quantum dot are performed numerically by employing the Runge-Kutta-Fehlberg method. The optical specifications of the structure are examined by using the compact-density-matrix formalism within iterative method. The total refractive index changes, the total absorption coefficients, the charge-currents and the induced magnetic fields are studied for different values of the energy dependency parameter.

Evaluation of the external electric- and magnetic field-driven Mathieu quantum dot’s optical observables

In this study, for the first time, the total refractive index changes (TRICs) and total absorption coefficients (TACs) of the quantum dot including the Mathieu potential confinement formed by the InxGa1−xAs/GaAs heterostructure under the influence of external electric and magnetic fields are theoretically investigated. The spectra and eigenfunctions of the Mathieu quantum dot are obtained using the effective mass approximation by forming a tridiagonal matrix formalism. The iterative method and compact-density-matrix formalism are used together to examine the nonlinear optical properties of the Mathieu quantum dot. Throughout the study, the effects on the TRICs and TACs of the external electric and magnetic field, as well as the In concentration and confinement width, are probed. Considering the strong and weak regimes of the external electric and magnetic fields, their alternatives to the structural parameters in terms of optical properties are also evaluated. The increment of the In concentration causes the quantum dot encompassment to turn into the opposite character after a certain radial distance. This result may be remarkable in terms of experimental applications. Under certain conditions, the incident optical intensities photons on the structure are determined at the limit values. As well as determining the functional range of the Mathieu quantum dot in terms of the TRICs and TACs characters, using both structure parameters and external fields and as a function of the incident photon energy, the determination of the optimum for these characters is an important theoretical gain in terms of providing a prediction for experimental studies.

Regulation of optical properties by applied external fields for a quantum well with Hulthen potential

In this present study, the effects of electric, magnetic, and non-resonant intense laser field (ILF) on the linear, third-order nonlinear, and total optical absorption coefficients (TOACs) and relative refractive index changes (RRICs) of GaAs quantum well, having Hulthen confinement potential, were theoretically investigated. In addition, the dependence of the nonlinear optical properties in the structure on the optical intensity of incident photon and the inverse relaxation time was also calculated. To do this research, firstly the energy eigenvalues and eigenfunctions of the structure were calculated by using the effective mass and envelope function approaches. By using these calculated subband energy levels and wave functions belonging to these levels, the nonlinear optical properties of the system were obtained via the iterative method, within the compact density matrix approach framework. The obtained numerical results show that the optical properties of the considered system depend on the externally applied fields. With the applied external electric and magnetic field, the peak positions of TOACs and RRICs shift to higher energies, and the peak magnitudes increase. The high-frequency ILF applied to the structure shifts the peak positions of TOACs and RRICs initially towards higher energies and then towards lower energies and their peak sizes increase. These results show that the optical properties of the system can be adjusted purposively by changing the magnitude of applied external fields.

Terahertz laser field manipulation on the electronic and nonlinear optical properties of laterally-coupled quantum well wires.

An intense terahertz laser field is shown to actively manipulate the electronic states, as well as the linear and nonlinear optical absorption coefficients, of the laterally-coupled quantum well wires (LCQWWs). The laser-dressed quantum states of the LCQWWs are achieved using the non-perturbative Floquet method and the two-dimensional diagonalization technique under the effective mass approximation. We have demonstrated that the intense terahertz laser field induces a strong deformation of the confinement potential configuration of the LCQWWs, thus pronouncedly dressing the energy levels and wave functions. An unambiguous picture is depicted for the evolution of the laser-dressed quantum states with the increase of the laser-dressed parameter characterizing the strength of the laser-dressed effect. On this basis, the resonant peak positions of the linear and nonlinear optical absorption coefficients feature a blue shift followed by a red shift with an increase of the laser-dressed parameter. Furthermore, the evolution of the peak values for the linear and third-order nonlinear optical absorption coefficients as a function of the laser-dressed parameter is comprehensively discussed. Moreover, in contrast to the case without intense terahertz laser field, the peak values of the linear, third-order nonlinear, and total optical absorption coefficients can be obviously enhanced at the same frequency position by manipulating the appropriate laser-dressed parameter. A similar feature can be found in the linear, third-order nonlinear, and total refractive index changes. Our findings are conducive to the implementation of the expected quantum states and nonlinear optical effects in the LCQWWs, paving the way for new designs in tunable optical switches, infrared photo-detectors and infrared modulators.

The Total Absorption Coefficient and Refractive Index Change of a Spherical Quantum Dot in the Confinement Radial Potential

The Total Absorption Coefficient and Refractive Index Change of a Spherical Quantum Dot in the Confinement Radial Potential

Optical Properties of Gaas/Alxga1-xas Superlattice Under E-Field for Quantum Cascade Laser Application

Optical properties of GaAs/AlxGa1-xAs superlattice are studied dependent on quantum well thickness of gain region and doping density of injector layers underperformed electric field. Conduction band alignment of the superlattice is obtained by using effective mass approximation. 1d-Schrodinger formula is solved by using FDM. Intersubband transition energies, linear (nonlinear and total) absorption coefficients and linear (nonlinear and total) refractive index changes are plotted under applied electric field intensity. Intersubband transition energy of electron from second excited state to first excited state shows 147 meV. It is found that -45 kV/cm electric field intensity and 5 nm layer thickness of last quantum well of the gain region are the best values for studied structure. After that, linear absorption coefficient is investigated dependent on carrier number in the injector region under electric field. It is found that carrier number over 5 𝑥 1016 𝑐𝑚−2 can causes huge internal absorption of the radiative emission obtained in gain region due to increase in linear absorption coefficient by factor 10. As a conclusion, total absorption coefficient and total refractive index change are calculated for optimized parameters.

Linear and nonlinear refractive index changes in monolayer MoSe2

In this work, we study the linear, the third-order nonlinear, and the total refractive index changes (RICs) caused by both intra- and inter-band transitions in monolayer MoSe2 in the presence of a magnetic field by using the compact density matrix approach. The results show that RICs display the blue-shift behavior with the increase of the magnetic field. The Zeeman fields do not affect the peak positions but reduce slightly peak intensities. Besides, the strong spin-orbit coupling in monolayer MoSe2 causes a significant difference in the peak due to spinning up and down. The RICs due to intra-band transition display only one peak in the THz range, while the inter-band spectra show a series of peaks in the near-infrared optical range, making monolayer MoSe2 be a promising candidate for novel optoelectronic applications.