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In the case of finite confinement potential, the average energies and corresponding wave functions for the 1s2nl configurations, in which nl = 2s, 2p, 3d, and 4f, of three‐electron GaAs/AlxGa1−xAs quantum dot with and without impurity are computed by using a new variational approach which is a combination of Quantum Genetic Algorithm procedure and Hartree–Fock–Roothaan method. Using the calculated average energies and wave functions, a detailed investigation of the linear, third‐order nonlinear and total absorption coefficients (ACs) and the refractive index changes (RICs) for the quantum dot is performed, and the obtained results are presented as a function of dot radius and photon energies. The results show that the dot radius, the impurity charge, and the height of potential barrier have a strong influence on the average energies and absorption spectra of the system. As the potential barrier height increases, the peak positions of the ACs and RICs shift toward higher energy, and there is a significant increase in the amplitudes of the absorption spectra as the potential barrier height increases. In addition, the electron wave functions begin to enter the quantum well at smaller dot radii with increasing barrier height. [ABSTRACT FROM AUTHOR]

In this paper, we theoretically investigate the electronic and optical properties of CdSe/ZnS quantum dots (QDs) of varying sizes. We calculate the energy eigenvalues and wave functions dependence on QD dimensions, temperature, and pressure using a combination of coordinate transformation and the finite difference method. We analyze the oscillator strength, transition lifetime, absorption coefficients (AC), and refractive index changes (RIC) for various values of dot sizes, temperature, hydrostatic pressure, and incident photon intensity. The results obtained indicate a strong dependence of electronic and optical properties on temperature, hydrostatic pressure, and the size of the nanostructure. The oscillator strength decreased with increasing hydrostatic pressure, but increased with rising temperature. Conversely, the transition lifetime exhibits an opposite trend. Furthermore, the total AC and RIC increase as incident optical intensity decreases. Linear, nonlinear, and total AC and RIC display a red shift with increasing hydrostatic pressure and a blue shift with rising temperature. [ABSTRACT FROM AUTHOR]

The current work focuses on investigating how various external and structural factors can affect the electronic structure and optical properties of a GaAs/Ga1−xAlxAs quantum ring. Specifically, we have studied the effects of spin–orbit interaction (SOI), pressure, temperature, and dimensions on the energy levels, dipole transition matrix elements (DTMEs), susceptibilities, optical absorption coefficients (OACs), refractive index changes (RICs), and group velocity of the quantum ring. These results show that the ground state energy of the system increases with the concentration of aluminum, while increasing temperature and ring size leads to a decrease in DTMEs due to a decrease in wave function overlap. We have also found that the presence of Rashba SOI, pressure, temperature, as well as the ring’s size dominate the electronic structure and subsequently affect the OACs and RICs of the system. A significant enhancement of the OACs can be witnessed when the Rashba coefficient and ring size are enlarged. Furthermore, the results represent a red shift with enhanced Rashba coefficient and relaxation time, whereas the growing ring size results in a blue shift in Optical sensitivities. Finally, we have analyzed the dependence of the group velocity of probe light pulses on the ring's size, photon frequency, and incident optical intensity. Our findings suggest that by controlling these parameters appropriately, it may be possible to achieve effective control of light speed, which could have interesting applications in electro-optical quantum communication networks. Overall, this work sheds light on the potential applications of these findings in the design and construction of spin-based devices and may offer new avenues for further research in this field. [ABSTRACT FROM AUTHOR]

This work presents a numerical study on the electronic and optical properties of modified Möbius squared potential well in the presence of static electric and magnetic fields. The potential well is formed within GaAs/AlGaAs hetero structures. Schrödinger's equation is solved within the framework of effective mass and envelope wave function approximations to get the wave functions and their corresponding energies of states. The optical absorption coefficients and relative refractive index changes are calculated via the expressions derived from the compact density matrix approach. The numerical results present strong blue shifts on the optical responses of modified Möbius squared potential well when the external electromagnetic fields are strengthening. [ABSTRACT FROM AUTHOR]

This numerical study scrutinizes the impact of both the thickness of layers and an externally applied magnetic field on the optical absorption coefficient and alterations in the refractive index pertaining to the intersubband optical transition (1-2) within an asymmetric double parabolic structure, utilizing GaAs/AlGaAs quantum wells as a basis. Energy levels and their corresponding wave functions have been ascertained through the use of the shooting method. The findings of this investigation suggest a pronounced sensitivity of the optical absorption coefficient and changes in the refractive index to the thickness of the layers and the applied external magnetic field. It has been observed that the intensification of the magnetic field results in a resonant peak position shifting towards higher energy values, whereas the thickness of the layers exerts an influence on the resonance peak magnitude. The insights derived from this study hold considerable potential for application, particularly in the development of optical devices predicated on intersubband electronic transitions. [ABSTRACT FROM AUTHOR]

We report the comparative investigation of fabricating type-II waveguide lasers in Nd:Y3Al5O12 (Nd:YAG) using femtosecond laser pulses at 515 and 1030 nm. We focus on the comparison in track morphologies, modification thresholds, and the overall efficiency of the ultrafast laser inscription (ULI) process in creating these waveguides. For both wavelengths, we demonstrated low propagation losses of 0.2 dB/cm. We achieved the lowest reported lasing threshold of 9 mW in a Nd:YAG waveguide laser. Superior performance was achieved with the 1030-nm ULI source, yielding a slope efficiency over 40% and achieving a lasing threshold at half the value observed for the 515-nm source. [ABSTRACT FROM AUTHOR]

In this paper, we measured M2 factor of a He–Ne probe beam initially with TEM00 mode influenced by thermal lens effect in liquid ethanol. The thermal lensing was induced by focusing a diode laser beam in ethanol. The results of this investigation show that when the diode laser power is increased, the beam quality factor M2 of He–Ne rises nonlinearly. The results of this study are useful for applications of laser ablation in liquid (LAL) in which beam quality and focused size at the target surface are crucial. According to our results, thermal lens effect induced by high-power laser beam can reduce the beam quality and must be considered in LAL and similar applications. [ABSTRACT FROM AUTHOR]

We explore the impact of external fields on the absorption coefficients and relative refractive index changes in a quantum cascade laser profile-like heterostructure that consists of a triple asymmetric quantum well. Firstly, we solve numerically the time-independent Schrödinger equation by using the diagonalization method under the effective mass and parabolic band approaches, to obtain the energy levels and wavefunctions. Then, we evaluate the optical coefficients from the analytical expressions derived from the compact density matrix method. The obtained results put forth that the resonant peaks of optical coefficients shift to higher (lower) energies by increasing the value of the electric (magnetic) field. These results indicate that it would be possible to adjust the optical properties of these structures to the desired range with external fields. As a result, we hope that new optoelectronic devices based on asymmetric triple quantum wells can be developed using the features found here. [ABSTRACT FROM AUTHOR]

This study delves into the optical characteristics of multilayered spherical quantum dots (MLSQDs). By employing the finite element method, we systematically explore the impact of varying layer dimensions, the A l -concentration, and the intersubband relaxation time on the linear, third nonlinear, and total optical absorption coefficients and refractive index changes within this nanostructure. Our findings reveal intriguing correlations between the sizes of individual layers and the resultant optical responses. Notably, subtle adjustments in layer dimensions manifest profound changes in both linear and third-order nonlinear absorption coefficients. Furthermore, the investigation of relaxation time elucidates the key role it plays in changing optical properties, illustrating how relaxation time influences the optical behavior of MLSQDs. This study provides a comprehensive understanding of the impact of layer sizes, relaxation time, and A l concentration on the optical properties of MLSQDs. These findings offer valuable guidance for engineering customized optical functionalities in nanophotonic technologies. • The OAC peaks shift red with increased core radius, then blue shifts at larger sizes. • The OACs and RICs generally follow the trends observed in the transition energy. • Higher relaxation times lead to stronger and sharper absorption peaks. • A l -concentration is another dimension to the control and tuning of QD properties.. [ABSTRACT FROM AUTHOR]

This study presents a detailed theoretical analysis of the effects of hydrostatic pressure, temperature, impurity factors, and external electric fields on the optical properties of In x Ga 1-x As tuned quantum dot. A uniform magnetic field, directed perpendicular to the quantum dot plane, is applied. The system is excited using a monochromatic electromagnetic field, considering electron intersubband transitions. Energy levels and wave functions are determined using the parabolic band approximation and effective mass approximation. The linear and nonlinear optical absorption coefficients and refractive index changes are computed using the compact-density matrix approach and the iterative method. Numerical results indicate that the peaks of the linear and nonlinear optical absorption coefficients and refractive index changes shift towards lower energies (red shift) and higher energies (blue shift) under varying hydrostatic pressure, temperature, and impurity factor strength. Additionally, the peak values of the absorption coefficients and refractive index changes increase or decrease based on these parameter variations. These results have significant implications for the design and optimization of quantum dot-based optoelectronic devices. • We study the optical absorption coefficients and refractive index changes for In x Ga 1-x As tuned quantum dot. • The energy levels and wave function are determined within the effective mass approximation. • The linear and non-linear optical absorption coefficients and refractive index changes, are computed using the compact-density matrix approach. • We find out that the peak of both linear and nonlinear optical absorption coefficients and refractive index changes, are shifted. [ABSTRACT FROM AUTHOR]

The optical absorption of the donor impurity in the two-dimensional GaAs quantum ring was studied with the effective mass approximation using the finite element method. The influence of the magnetic field, light intensity, and impurity position on the optical absorption coefficient is analyzed. The results reveal that the application of a magnetic field can increase the peak value of the absorption coefficient and cause a blue shift phenomenon. With the increase of light intensity, the peak splitting in total optical absorption appears. With the increase of the distance between the impurity and the center of the quantum ring, the spacing of the energy level decreases, resulting in a decrease in the peak value of the total absorption coefficients, and a red shift occurs. On the other hand, when the impurity is located between the inner and outer radius, the opposite effects appear as the impurity is far from the center of the quantum ring. [ABSTRACT FROM AUTHOR]

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. • Solved the radial SE using screened Kratzer potential employing the NUFA method. • Resulted in analytical expressions for energy eigenvalues and associated eigenfunctions. • We observe that the optical response are highly sensitive to dot size and potential parameters. • Explored the impact of external magnetic and AB flux fields on the optical properties. • Provides insights for the design and optimization of quantum dot-based optoelectronic devices. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

The laser field effects on the electronic and optical properties depending on two different positions in the plane of GaAs/Al (GaAs) quantum wire with square cross sections have been investigated. The electron energy levels and the electronic wave functions of the wires are calculated using the finite differences method within the effective mass approximation. The differences of the total absorption coefficients and the reflection index changes sourced from the cross-sectional shape were determined and explained with and without laser field. From the results the blue shift and red shift effects on the total absorption coefficients and the reflection index changes were identified depending on the laser field strength and the positions of square GaAs/Al(GaAs) quantum well wire in the plane. [ABSTRACT FROM AUTHOR]

Optical properties of a spherical quantum dot (QD) with an on-center hydrogenic impurity in the external static magnetic field are studied. Energies and wavefunctions of the impurity electron are calculated using the Lagrange mesh method. Expressions for the optical absorption coefficients (ACs), refractive index changes (RICs) and group index (GI) are derived with the help of the density matrix formalism for a two-level system, and analyzed from the theoretical point of view. The behavior of ACs, RICs and GI with respect to the incident photon energy is examined, as well as their dependence on the magnetic field strength, laser intensity and relaxation time. It is observed that all of these parameters strongly affect the studied properties of the QD. • The Hamiltonian eigenproblem of the spherical quantum dot with H impurity is solved by using the Lagrange mesh method. • The effect of the magnetic field and QD radius on ACs, RICs and GI is studied. • The influence of the laser intensity and relaxation time on ACs, RICs and GI is also investigated. • Graphically illustrated the possibility of subluminal and superluminal propagation of laser light. [ABSTRACT FROM AUTHOR]

In the present work, we are interested for an isolated and self-assembled InAs/InP quantum dots with a dome cross-section. We have tried to study the electronic and optical properties in the quantum dot by using an efficient and simple method. This numerical method is based on the coordinate transformation and the finite difference method (FDM). The influence of the parameters introduced in the mathematical function, is studied on the size, the shape and the number of the quantum dot. The electron, and heavy hole energy levels as well as their interband transition energies are also investigated. The linear, third-order nonlinear and total interband optical absorption coefficients and refractive index changes are investigated as a function of photon energy with varying height dot (H) and the incident optical intensity (I). The analytical expressions of these optical properties are obtained by using the compact-density matrix formalism. [ABSTRACT FROM AUTHOR]

In this paper, we study the effect of energy-dependent effective mass on optical properties of GaAs/GaxIn1−xAs and GaAs/AlxGa1−xAs quantum well systems through the compact density matrix approach. We solved the resulting nonlinear Schrödinger equation by a simple shooting method and present the algorithm. We show that the energy-dependent effective mass effect is more important for systems with narrower quantum well systems. By an energy-dependent effective mass assumption, absorption coefficient peak height increases with increasing the total system length L while in the constant effective mass limit, absorption coefficient peak heights have not been influenced by changing L. In the GaAs/AlxGa1−xAs system, by increasing the number of wells, the linear absorption coefficient amplitude at first increases and then decreases in the fixed effective mass approximation and monotonically decreases in the energy-dependent effective mass case. By increasing the number of wells, the linear absorption coefficient peak position at first shows a blue shift and then shows a redshift. In the GaAs/GaxIn1−xAs system, the situation is more complicated and it is described in more detail in the text. However, GaAs/GaxIn1−xAs quantum well systems have larger values of absorption coefficient peak heights than GaAs/AlxGa1−xAs ones. [ABSTRACT FROM AUTHOR]

In this paper, we present a multiphysics modeling of rare earth-doped cladding-pumped fiber amplifiers to predict the device performance with respect to the constraints associated with space missions. By combining the 3-D nonhomogeneous heat conduction equation with the nonlinear rate equations, the developed numerical algorithm makes possible the calculation of the spatial distribution of the different optical signals and temperature profiles. The temperature dependence of the refractive index, emission, and absorption cross sections, as well as the radiation induced attenuation and the lifetime versus the deposited dose have been considered, too. They lead to the optical signals changing inside the fiber creating a feedback loop that influences the temperature distribution within the fiber. Different operational regimes for a representative fiber design as well as different cooling configurations have been investigated. The obtained numerical results highlight that the thermal field inside the fiber could strongly deteriorate the amplifier performance especially in the space radiation environment. [ABSTRACT FROM AUTHOR]

The impact of vertical electrical field on the electron related linear and 3rd order nonlinear optical properties are evaluated numerically for pyramidal GeSn quantum dots with different sizes. The electric field induced electron confining potential profile’s modification is found to alter the transition energies and the transition dipole moment, particularly for larger dot sizes. These variations strongly influence the intersubband photoabsorption coefficients and changes in the refractive index with an increasing tendency of the 3rd order nonlinear component with increasing both quantum dot (QD) size and applied electric field. The results show that intersubband optical properties of GeSn quantum dots can be successively tuned by external polarization.

Effects of applied magnetic field, temperature and dimensions on the optical absorption coefficients (AC) and refractive index (RI) changes of a GaAs quantum ring are investigated in the presence of both Rashba and Dresselhaus spin-orbit interactions (SOI). To this end, the finite difference method (FDM) is used in order to numerically calculate the energy eigenvalues and eigenstates of the system while the compact density matrix approach is hired to calculate the optical properties. It is shown that application of magnetic field, temperature as well as the geometrical size in the presence of spin-orbit interactions, alter the electronic structure and consequently influence the linear and third-order nonlinear optical absorption coefficients as well as the refractive index changes of the system. Results show an obvious blue shift in optical curves with enhancing external magnetic field and temperature while the increment of dimensions result in red shift. [ABSTRACT FROM AUTHOR]

Tools of mathematical modeling provide a great opportunity in order to investigate semiconductor nanostructures with a conclusive objective of predicting their behavior and understanding of their limits. While most numerical and analytical investigations deal with the pure Rashba interaction, this article will study the absorption coefficient and refractive index changes of a lens-shaped GaAs quantum dot in the presence of simultaneous Rashba and Dresselhaus spin–orbit couplings under the effects of applied electric and magnetic fields. It is shown that applying magnetic field, in the presence of spin–orbit interactions, removes the degeneracy and split the energy levels into two branches and by enhancing the field, absorption coefficient and refractive index changes related to transition between the ground and second excited states ( E 31 ) move towards lower photon energies (red shift). It is also revealed that by increasing the applied electric field a blue shift in optical curves can be detected. [ABSTRACT FROM AUTHOR]

Photo-thermo-refractive (PTR) glass is an optically transparent photosensitive multicomponent silicate glass. UV-exposure produces silver nanoclusters, and NaF nanocrystals upon heating, giving rise to permanent refractive index changes. This is the basis for the production of Bragg gratings. In this article, we present a comprehensive overview of the photo-thermo-induced effects in PTR glass. We first give a general introduction of PTR glasses and their applications. Then, we perform a thorough analysis of the mechanisms of refractive index changes starting with the photo-induced process followed by the crystal nucleation mechanism and NaF crystallisation kinetics. Finally, we concentrate on the PTR glass nanostructure and its effect on the crystallisation mechanisms and properties, finishing with the kinetics and origin of the refractive index change. Despite the fact that much is known about this septuagenarian glass and that it is already being commercially produced, a number of open problems still exist that warrant further investigation. [ABSTRACT FROM PUBLISHER]

In this study, the effect of position-dependent effective mass (PDM) on the nonlinear optical properties in a GaAs/AlAs semiconductor quantum well (QW) are intensively studied. Calculations are performed using both the position-dependent effective mass and a constant effective mass within the framework of the compact-density-matrix approach, iterative method, and coordinate transformation method. We have calculated the third-harmonic generation (THG) coefficients, the optical absorption (OA) coefficients and the refractive index changes (RIC) as a function of the incident photon frequency and obtained the energy eigenvalues and eigenfunctions of the system through solving the Schrödinger equation. The results show that spatially varying electron effective mass has a significant impact on the nonlinear optical properties in a quantum well. [ABSTRACT FROM AUTHOR]

In this paper, the nonlinear optical properties of a hybrid system composed of metal nanoparticles (MNP) and Zigzag quantum wells (ZQWs) is discussed. A controlled laser field is applied to induced dipole moments in MNP and ZQWs, the induced dipole moment produced by the hybrid system transforms the energy interval and the spontaneous decay rate of ZQWs. The energy level and wave function of ZQWs in the hybrid system is obtained by employing finite difference method. The analytical expressions of optical absorption coefficients (OACs) and refractive index changes (RICs) are acquired through the method of the compact density matrix method and iterative approach. The outcomes reveal that the nonlinear optical properties of the hybrid system are modulated by the size of MNP and the center-to-center distance between MNP and ZQWs. • The modulation of optical coefficient by metal nanoparticles is given. • The effect of surface plasmon on quantum well parameters is analyzed. • The effect of metal nanoparticles on quantum well modulation is discussed. [ABSTRACT FROM AUTHOR]

The optical absorption coefficients (OACs), refractive index changes (RICs), and electronic states in konwent-like quantum well under the effects of silicon impurities were studied within the framework of the effective mass approximation (EMA). Firstly, the subband energy levels and their probability densities are determined by solving Schrödinger-Poisson equations iteratively. Once these quantities are computed, we have addressed different OACs and RICs (linear and nonlinear) between the ground and the first excited levels. We have considered two positions of the silicon-doped layer. The first one is at the center of the structure and the second one is inside the left potential well. Our findings indicate that in the case of doping at the center, an increase in the concentration of the doped layer reduces the energy levels of the ground and the first excited states. However, when the doped layer is moved to the left well, its concentration increase augments the energy of the first excited state and diminishes that of the ground state. This behavior of energy levels and wavefunctions is attributed to the newly created triangular well around the doped layer. Moreover, the impact of the structural parameters and their impact on the red/blue shift of the (OACs) and (RICs) have been discussed in detail. As a consequence, the concentration and position of the doped layer as well as the structural parameters constitute an important tool to modify the shape of the confining potential which leads to additional control of the energy states and optical properties of different heterostructures based on konwent-like quantum wells. • We study the optical absorption coefficients in konwent-like quantum well. • The optical absorption coefficients and refractive index changes depend on the doping layer concentration and its location. • The self-consistent resolution is employed to compute the energy levels and wavefunctions. [ABSTRACT FROM AUTHOR]

Intersubband optical transitions, refractive index changes, and absorption coefficients are numerically driven for direct bandgap strained GeSn/Ge quantum dots. The linear, third-order nonlinear and total, absorption coefficients and refractive index changes are evaluated over useful dot sizes’ range ensuring p-like Γ-electron energy state to be lower than s-like L-electron energy state. The results show strong dependence of the total absorption coefficient and refractive index changes on the quantum dot sizes. The third order nonlinear contribution is found to be sensitive to the incident light intensity affecting both total absorption coefficient and refractive index changes, especially for larger dot sizes.

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. • The hydrostatic pressure and temperature affecting the effective mass of electron. • The quantum size parameter and limiting potential parameter affecting OACs and RICs. • peak and resonant peak of OACs and RICs vary with the above factors. [ABSTRACT FROM AUTHOR]

The influence of position-dependent mass (PDM) on nonlinear optical absorption (OA) coefficients and refractive index changes (RICs) is theoretically studied, within the framework of the iterative method and the compact-density-matrix approach. Through solving Schrödinger equation, the eigenfunctions and energy eigenvalues are obtained. The analytic expressions of the optical absorption coefficients and the refraction index changes are derived theoretically. The results reveal that the OA coefficients and the RICs are strongly affected by PDM, and both the peaks of them increase when considering PDM. [ABSTRACT FROM AUTHOR]

We have intensively studied the influence of the shape of quantum dots on the refractive index changes. Within the framework of the effective-mass approximation, numerical results are performed by means of calculation methods of the compact-density-matrix and the matrix diagonalization. We analyze the properties of the linear, third-order nonlinear and total refractive index changes (RICs) as a function of the incident photon energy in circular, elliptic, and triangular shaped quantum dots. The results show that the shape of quantum dots has a significant impact on the refractive index changes. [ABSTRACT FROM AUTHOR]

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 (L w L), whilst a red shift is noticed when changing left and right wells (L w L and L w R) and barrier (L b L and L b R) widths for zero fields. We believe that our study could make a contribution to designing new quantum-well-based optoelectronic devices. [ABSTRACT FROM AUTHOR]

In this present study, the effect of electron-LO-phonon interaction on the refractive index changes (RICs) in a Modified-Pöschl–Teller quantum well (QW) is theoretically investigated within the framework of the compact density matrix approach and iterative method. The energy eigenvalues and their corresponding eigenfunctions of the system under the influence of electron-LO-phonon interaction are calculated with the non-degenerate perturbation method. The results show that the RICs are strongly affected by the well depth and well width of the QW system. Moreover, the theoretical values of the RICs are obviously increased when considering the electron-LO-phonon interaction. [ABSTRACT FROM AUTHOR]

The nonlinear optical properties in square tangent quantum wells are studied theoretically. We obtain eigenfunctions and energy eigenvalues by means of solving Schrödinger equation within the framework of effective mass approximation. Using the compact-density-matrix approach and iterative method, the analytic expressions of the third-harmonic generation (THG) coefficients, the optical absorption (OA) coefficients and the refractive index changes (RIC) are obtained. The results show that the THG coefficients are affected by d and U 0 , while the OA coefficients and the RIC are strongly affected not only by d and U 0 but also by the incident optical intensity. [ABSTRACT FROM AUTHOR]

Excitonic effects on linear and nonlinear optical absorption coefficients (OAC) and refractive index changes (RIC) in one-dimensional quantum dots with linear potential are theoretically investigated within the framework of the compact-density-matrix approach and iterative method. It is found that linear and nonlinear OAC and RIC with excitonic effects in one-dimensional quantum dots are larger than that without excitonic effects. Besides, when excitonic effects are considered, our results show a remarkable dependence of linear and nonlinear OAC and RIC on linear potential. [ABSTRACT FROM AUTHOR]

In the present work, the effects of the intense laser field on total optical absorption coefficient (the linear and third-order nonlinear) and total refractive index change (the linear and third-order nonlinear) for transitions between different intersubbands in the Ga 1− x Al x As/GaAs cylindrical quantum dot under external electric field are investigated. The calculations were performed within the compact density-matrix formalism with the use of the effective mass approximation. The obtained results show that both total absorption coefficient and refractive index change are sensitive to the electric and intense laser fields. By changing the intensities of the electric and laser fields, we can obtain the blue or red shift, without the need for the growth of many different samples. [ABSTRACT FROM AUTHOR]

In this study, the intersubband optical absorption coefficients and the refractive index changes are calculated in a square quantum well (SQW), a parabolic quantum well (PQW), a graded quantum well (GQW) and a V-shaped quantum well (VQW), without and with the intense laser field (ILF). Our results show that the position and the magnitude of the linear, nonlinear and total absorption coefficients and refractive index changes depend on ILF parameter and the quantum well (QW) shape. While for SQW the intersubband absorption spectrum shows blue shift up to the critical ILF value, this spectrum shows red shift for greater ILF values than this certain value. Whereas, for PQW, GQW and VQW the absorption spectrum shows always red shift by increasing ILF. Thus, the intersubband absorption coefficients and the refractive index changes which can be suitable for great performance optical modulators and multiple infrared optical device applications can be easily obtained by tuning ILF value and QW shape. [ABSTRACT FROM AUTHOR]

It is well-known that the optical properties of semiconductor nanostructures are so sensitive to alteration of confinement while the nanostructure’s morphology often determines the confinement. Accordingly existence of a bulge on the wire surface will affect the specifications of the nanowire. However, bulge existence effects are significant for ultrafine nanowires and negligible for wires with large radius. In the present work we consider a GaAs ultrafine nanowire with a bulge on the middle of wire axis. The linear, third-order nonlinear and total absorption coefficient and refractive index changes variations are investigated as functions of bulge and nanowire radius. Also the effects of bulge and wire radius on saturation are studied. It has been found that increment in wire (bulge) radius leads to a red shift (blue shift) in absorption coefficient and refractive index changes curves. Additionally, alteration of wire and bulge radii, changes the corresponding incident photon intensity that saturation occurs at it. [ABSTRACT FROM AUTHOR]

The linear and nonlinear anisotropic optical absorption coefficients(OACs) and refractive index changes(RICs) of GaN/AlN cubical quantum dots(CQDs) subjected to terahertz laser field(TLF) are investigated. The results show that under the polarization of TLF, with the increase of laser dressing parameters, the peak of OACs and RICs increases nonlinearly and have a redshift. More importantly, our work indicated that with the enhancement of TLF polarization, the redistribution of electron excited state wave function will lead to the "loss" of optical properties in the specific frequency band. The redistribution of electron ground state wave function has a significant modulation effect on the magnitude of OACs(RICs) peak. • The enhancement of the refractive index changes was observed at low frequencies. • The phenomenon of wave function exchange in laser field modulation is found. • The modulation of laser field on optical coefficient cannot cover the whole frequency band. [ABSTRACT FROM AUTHOR]

In this paper, we have investigated the effect of the well number and quantum ring thickness on subband energies, intersubband transition energy and linear and nonlinear optical properties of a two electron / constant total effective radius multi-shells quantum rings (CTER-MSQRs). Effect of well number increase on linear and third order absorption coefficients and refractive index changes is not monotonic, while if inner ring radius R0 increases absorption coefficient monotonically decreases. Absorption peak positions have no red/blueshifts when well number or inner quantum ring radius R0 increase. When well number increases, the amount of nonlinearity monotonically decreases. Finally, six-wells CTER-MSQR has minimum nonlinearity. [ABSTRACT FROM AUTHOR]

In this work we have investigated the effect of external electric field on the electronic structure and refractive index changes of a GaN/AlN constant total effective length multiple quantum well. A decreasing oscillatory behavior for energy levels was seen when the electric field increased and in some energy values the energy levels intersected. By increasing the number of wells, oscillator strength dropped suddenly and moved to higher electric field in a critical electric field. By using the number of wells and the total length of the structure as two tuning tools, we were able to select our previously determined critical electric field. [ABSTRACT FROM AUTHOR]

Abstract: The binding energies and corresponding wave functions of ground and first excited states (1s, 2p) of on-center hydrogenic donor and acceptor impurities are calculated using finite difference approximation in the effective mass framework. The on-center impurities are assumed to be in an InAs spherical quantum dot which is located at the center of a GaAs cylindrical nano-wire. To test the validity of applied method the eigenvalues of ground and first excited states are compared with reported results which have been calculated by finite element methods and it is shown that the finite difference approximation is more accurate in this particular case. In addition, the oscillator strength, linear, third-order nonlinear and total optical absorption coefficients and refractive index changes have been calculated for 1s–2p transition by means of the compact density matrix approach. The results show that presence of impurity causes a blue shift in optical spectrum which is larger for acceptor impurity. Also, the amplitude of absorption coefficient, refractive index changes and oscillator strength depend on the absence, presence and type of impurity. Moreover, it is found that the saturation condition can be tuned by type of impurity and critical incident optical intensity is enhanced in presence of acceptor impurity. [Copyright &y& Elsevier]

Abstract: An investigation is done in order to calculate the linear, third-order nonlinear and total optical absorption coefficient and refractive index changes of an impure GaAs spherical quantum dot placed at the center of a cylindrical nano-wire. In this regard, the finite difference approximation is considered to calculate electronic structure as well as compact density-matrix approach is applied to investigate optical properties. In this study the effects of laser-field radiation along with aluminum (Al) concentration on optical properties are examined for three transitions between four first lower-lying electronic levels, i.e. , and transitions. Also the effect of relaxation time on saturation is studied and compared for these transitions. It is found that the magnitude of linear and third order nonlinear absorption coefficient and refractive index changes as well as the optical saturation can be modified by both Al concentration and the amplitude of laser-field radiation. Moreover, for transition ( transition) the effect of quantum dot (nano-wire) is dominant whereas for transition Al concentration is a major determinant factor. Additionally, for all transitions by increasing the value of laser field a red shift appears in optical spectrum where the extent of this red shift depends on the Al concentration and the energy levels between which the transitions occur. Finally, in contrast to QDs, a red shift appears in absorption spectrum as going up the transitions between higher energy levels. [Copyright &y& Elsevier]

The optical absorption coefficients (OACs) and refractive index changes (RICs) in the GaAs/Ga 1 − x Al x As 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. [ABSTRACT FROM AUTHOR]

Linear, nonlinear, and total absorption coefficient and refractive index changes of double-quantum well (DQW) systems are studied theoretically in the presence of external static electric field applied along the growth direction. The analytical expression for the linear and nonlinear optical properties is obtained using density matrix method. Emphasis is laid on the effect of asymmetry in the shapes of DQW system on optical properties. Some interesting results are obtained and explained. [ABSTRACT FROM AUTHOR]