Non-resonant Intense Laser Field Research Articles

Optical properties of n-type asymmetric triple δ-doped quantum well under external fields

We present a theoretical investigation about the the influence of external electric, magnetic and non-resonant intense laser fields on intersubband-related second harmonics generation (SHG) and the nonlinear optical rectification (NOR) coefficients in n-type asymmetric triple δ-doped quantum wells (QWs). A particular design of asymmetric triple δ-doped QW with Lw = 200 Å width and, respectively, in the left side, central and right side, and doping concentrations is taken into account. For QWs under the combined effect of the external electric, magnetic and laser fields, the time-dependent wave equation is modified by using Kramers-Henneberger transformation and the dipole approximation. The subband energy spectra and the electronic wave functions are obtained by solving numerically the wave equation. The originality of this work can be presented as; (i) The results explain NOR and SHG characteristics of triple QW depending on external field effects in detail. The effects of the electric, magnetic and laser field on transition energies and NOR, SHG characteristics are presented detail. (ii) In addition to, the alternativeness to each other of the external fields is discussed by probing the features of SHG and NOR under the strong and weak regimes of external fields. (iii) These nonlinear optical responses to the external fields are compared, researching the optimum cases for these optical specifications. (iv) The control of SHG through the external fields in triple δ-doped QWs reveals to be easier and more precise.

Impurity-related optical response in a 2D and 3D quantum dot with Gaussian confinement under intense laser field

ABSTRACTUsing the two-dimensional (2D) diagonalisation method, the impurity-related electronic states and optical response in a 2D quantum dot with Gaussian confinement potential under nonresonant intense laser field are investigated. The effects of a hydrogenic impurity on the energy spectrum and binding energy of the electron and also intersubband optical absorption are calculated. The obtained numerical results show that the degeneracies of the excited electron states are broken and the absorption spectrum exhibits a redshift with the values of the laser field. The findings indicate a new degree of freedom to tune the performance of novel optoelectronic devices, based on the quantum dots and to control their specific properties by means of intense laser field and hydrogenic donor impurity. Using the same Gaussian confinement model, the electronic properties of a confined electron in the region of a spherical quantum dot are studied under the combined effects of on-centre donor impurity and a linearly polarised intense laser radiation. The three-dimensional problem is used to theoretically model, with very good agreement, some experimental findings reported in the literature related to the photoluminescence peak energy transition.

Effect of the High-Frequency Laser Radiation on the Nonlinear Optical Properties of n-Type Double δ-Doped GaAs Quantum Wells.

In the present work, the effect of non-resonant intense laser field on the nonlinear optical rectification and second and third harmonic generation of n-type double δ-doped GaAs quantum well is studied in detail. The energy eigenvalues and eigenfunctions of this structure are calculated within the framework of effective mass and envelope function approximations. Analytic formulas for the coefficients of nonlinear optical rectification and second and third harmonic generation are obtained using the compact-density matrix approach (CDMA) and iterative method. Based on this model, our obtained numerical results are reported as a function of incident photon energy for several values of non-resonant intense laser field. The results show that the coefficients of nonlinear optical rectification and second and third harmonic generation are strongly affected by the non-resonant intense laser field.

Intense laser-induced electronic and optical properties in double finite oscillator potential

ABSTRACTIn the present paper, a theoretically study of the non-resonant laser field effect on the optical response, such as nonlinear optical rectification (NOR), second (SHG) and third harmonic generation (THG) coefficients in double finite oscillator potential (DFO) quantum wells is performed in the framework of the effective mass approximation. The obtained results reveal that, energy states and optical response is significantly affected by the non-resonant intense laser field (ILF) intensity and symmetry of the structure. Also it was found that the laser field is more effective on the optical response in the DFO potential when the asymmetric character of the confinement potential is strong. Thus, the NOR, SHG and THG coefficients with designated values can be obtained by using a properly adjusted ILF intensity and symmetry parameter of confinement potential.

Magnetic field effects on intraband transitions in elliptically polarized laser-dressed quantum rings

The combined influence of externally applied magnetic and non-resonant intense laser fields (ILF) on the electronic states of GaAs-based two-dimensional circular quantum rings is investigated. The behavior of the electron energy levels as a result of the variation in the strength of the external fields is studied. In particular, the effects of changing the polarization of the intense laser radiation on the conduction band potential profile and allowed energy levels are discussed in detail. The intraband transition energies and the dipole matrix elements are analyzed as functions of the applied magnetic field intensity for different combinations of the intense laser field and resonant probe laser radiation polarizations. The findings can be summarized as follows: i) the quantized energies steadily increase as functions of the magnetic field and ILF-effects, ii) the electric dipole matrix elements are larger for the case of circular non-resonant ILF-polarization and circular laser probe polarization with respect to the case of linear polarized radiation, and iii) the dipole matrix elements have oscillatory behavior due to the complex nature of the wave functions which stems from the imaginary term appearing in the Hamiltonian when magnetic field effects are included.

Effect of applied external fields on the nonlinear optical properties of a Woods-Saxon potential quantum well

In this present work a detailed theoretical study on the influence of the static electric, magnetic, and non-resonant intense THz laser fields on the nonlinear optical properties such as nonlinear optical rectification (NOR) and second harmonic generation (SHG), of a quantum well that has the Woods-Saxon potential profile. The static electric and high-frequency intense THz laser fields are applied along the growth-direction of the structure whilst the static magnetic field is applied perpendicular to them. The outcome of the numerical calculation demonstrates that, both the peak potions of the NOR and SHG coefficients exhibit a blue-shift with the increment of the static electric and magnetic fields, but their peak amplitudes increases with the magnitude of the electric field whilst decreases with the magnitude of the magnetic field. However, the peak positions of the NOR and SHG coefficients exhibit firstly a blue-shift, and then a red-shift with the increment of the laser intensity, but their peak amplitudes increases. We hope that these theoretical results will be useful for designing new optoelectronic devices with a performance tailored by the adjustment of the applied fields.

Hydrogenic donor impurities in -doped cylindrical quantum dots under intense laser field

A theoretical study of the effects of non-resonant intense laser field on the donor impurity binding energy in a cylindrical quantum dot with -doped axial potential is performed in the framework of the effective mass approximation. The obtained results indicate that, 2D impurity concentration and intense laser field intensity have a significant effect on the impurity binding energy and energy levels of electrons in the cylindrical quantum dots with -type axial potential.

Hydrostatic Pressure and Temperature Effect on the Electron-Related Optical Responses in Symmetric and Asymmetric n-Type Double Delta-Doped GaAs Quantum Well Under Terahertz Laser Field

The effects of non-resonant intense laser fields on the intersubband-related light absorption and relative refractive index change coefficients in symmetric and asymmetric n-type double $$\delta$$ -doped GaAs quantum wells are investigated. Systems are assumed to be also under the influence of hydrostatic pressure and the change of temperature. The single band effective-mass and envelope function approximations, together with analytical expressions for the linear and third-order nonlinear optical coefficients are used as theoretical tools. According to the numerical outcome, the nonlinear optical response is significantly affected by the intense non-resonant laser radiation, as a result of the associated distortion of conduction band energy profiles. For instance, it is revealed there is a laser-induced transition of the confining potential from double-delta geometry to single-triangular-like shape. Given the additional variations associated with the application of hydrostatic pressure and temperature, all these external probes could be used to control and suitablly tune the electronic and optical properties of GaAs n-type double $$\delta$$ -doped GaAs quantum wells.

Electronic states in GaAs-(Al,Ga)As eccentric quantum rings under nonresonant intense laser and magnetic fields

The features of the electron energy spectrum in eccentric two-dimensional GaAs-AlGaAs quantum rings of circular shape are theoretically investigated taking into account the effect of externally applied magnetic and intense laser fields. Analytical expressions for the laser-dressed confining potential in this kind of quantum ring geometry are reported for the first time. Finite element method is used to solve the resulting single-particle effective mass two-dimensional partial differential equation. It is shown that the allowed level spectrum is greatly influence by the external probe as well as by the breaking of geometric symmetry related to the changes in eccentricity. In presence of an intense laser field, the conduction band confining profile suffers strong modifications along the structure, with an additional contribution to symmetry breaking. These modifications of electronic quantum states reflect in the intraband optical absorption. Accordingly, the features of the intraband transitions are discussed in detail, revealing the significant influence of the magnetic field strength and laser field intensity and polarization, together with eccentricity, in the allowing of ground-to-excited states transitions and their corresponding intensities.

Morse quantum well modulated by nonresonant intense laser field: Binding energy and optical absorption related to shallow donor impurities

Binding energies of the lowest two s-symmetric impurity states and linear, third order nonlinear, and total optical absorption coefficients corresponding to the 1s → 2s transitions for electrons in a Morse quantum well are investigated. Influence of a non-resonant intense laser field is considered for different values of the structure parameter, impurity position, and laser field intensity. In order to find the eigenvalues and eigenfunctions of the unbound electron confined within the Morse quantum well under the intense laser field, the time independent Schrödinger equation is solved by using the effective mass and parabolic band approximations. The impurity binding energy is determined by means of a variational procedure, using hydrogen-like trial wave functions, and the optical response is treated with the use of a two-level approach in the density matrix expansion. Our results show that it is possible to design suitable devices described by a Morse-like confinement pattern in the desired wavelength by changing the mentioned parameters.

Electron-related optical responses in triple δ-doped quantum wells

ABSTRACTA detailed theoretical study on the electron-related optical responses in triple δ-doped GaAs quantum wells in the presence of non-resonant, monochromatic intense laser field is presented. For this purpose, we first obtained the bound subband energy levels and their corresponding envelope wave functions of the structure for different central doping concentrations within the effective-mass approximation. Then, we calculate the effect of the non-resonant intense laser field on the optical properties of this structure using the compact-density-matrix approach via the iterative method. We found that the optical absorption coefficients and refractive index changes in the triple δ-doped GaAs quantum well can be modulated by changing the central doping concentration and the intensity of the non-resonant, monochromatic laser field. In addition, it is shown that a sufficiently intense laser field suppresses the multiple quantum well configuration towards a single potential well one and the optical response becomes practically independent of the δ-doping concentration.

Linear and nonlinear optical properties in the terahertz regime for multiple-step quantum wells under intense laser field: Electric and magnetic field effects

We present a theoretical study on the linear and nonlinear optical properties in AlrGa1-rAs/GaAs asymmetric multiple step quantum wells (AMSQW) under the effects of a non-resonant intense laser field (ILF), electric, and magnetic field. Calculations are for the linear optical absorption and refractive index relative changes combined with the second and third harmonic generation. The potential profile is constructed as a function of the Aluminum concentration, so that the heterostructure has four steps of different concentration, width and height. The energy levels and corresponding wavefunctions are obtained by solving the Schördinger equation, for an electron, in the envelope function approach, with parabolic bands, and the effective mass approximations. The results show that variations in ILF, electric field and magnetic field have significant influences on the magnitude and peak energy positions of the SHG and THG coefficients. Therefore, we can conclude that the effects of ILF, electric and magnetic fields can be used to tune and control the SHG and THG in the range of the terahertz electromagnetic spectrum.Keywords: Multiple-step quantum wells; Linear optical properties; Second and third harmonic generation; Terahertz radiation; Intense laser field; Electric and magnetic fields.

Electron-related optical responses in Gaussian potential quantum wells: Role of intense laser field

A theoretical study of the effects of non-resonant intense laser field on the optical response in a Gaussian potential quantum well is performed in the framework of the effective mass approximation. The obtained results indicate that, the depth and range of the considered confinement potential and intense laser field intensity has a significant effect on the optical properties in Gaussian potential quantum wells. Also it was found that the laser field is more effective on the optical response in Gaussian potential quantum wells with smaller range.

Impurity-related optical response in cylindrical quantum dots with a δ-doped axial potential under an intense laser field

A theoretical study of the effects of a nonresonant intense laser field on the absorption coefficients and refractive index changes for a two-level system associated with transitions from the 1S -like impurity state to the 2Pz -like impurity state in a cylindrical quantum dot with a δ-doped axial potential is performed in the framework of the effective mass approximation. It is found that the nonresonant intense laser field and axial impurity position have obvious effects on the transition matrix elements and also on the difference between the electron densities of the states in cylindrical quantum dots, which are related to the refractive index changes and optical absorption coefficients.

The effects of intense laser field on optical responses of n-type delta doped GaAs quantum well under applied electric and magnetic fields

This work presents the results of the theoretical study of the effects of non-resonant intense laser field, electric and magnetic fields on optical responses of GaAs n-type δ-doped quantum well associated to the electron transitions. Optical properties are obtained by using the compact-density matrix method. The numerical results show that the applied external fields have a significant effect on the optical characteristics of these structures, such as the optical absorption coefficient and refractive index. Thus, such futures can be use to tune the optical properties of doped semiconductor heterostructures.

Nonlinear optical properties of asymmetric n-type double δ-doped GaAs quantum well under intense laser field

The effect of non-resonant intense laser field on the intersubband-related optical absorption coefficient and refractive index change in the asymmetric n-type double δ-doped GaAs quantum well is theoretically investigated. The confined energy levels and corresponding wave functions of this structure are calculated by solving the Schrodinger equation in the laser-dressed confinement potential within the framework of effective mass approximation. The optical responses are reported as a function of the δ-doped impurities density and the applied non-resonant intense laser field. Additionally, the calculated results also reveal that the non-resonant intense laser field can be used as a way to control the electronic and optical properties of the low dimensional semiconductor nano-structures.

Combined effects of the intense laser field, electric and magnetic fields on the optical properties of n-type double δ-doped GaAs quantum well

In the present work, the effects of the non-resonant intense laser field, electric and magnetic fields on the optical properties, such as linear, third order nonlinear and the total optical absorption coefficient and refractive index changes associated with the intersubband transitions between the ground and the first excited states in the n-type double δ-doped GaAs quantum well is theoretically studied by solving the Schrödinger equation in the laser-dressed confinement potential within the framework of effective mass approximation. The analytical expressions of the linear and third-order nonlinear optical absorption coefficients and refractive index changes are obtained by using the compact-density matrix formalism. Our numerical results show that the optical absorption coefficient and refractive index change are quite sensitive to the applied external fields, such as non-resonant intense laser field, electric and magnetic fields. The obtained results can be applied for the design of various optoelectronic devices based on the intersubband transitions of electrons.

The effects of the intense laser field on the optical properties of the asymmetric parabolic quantum well

We have calculated the effects of the intense laser field on the total optical absorption coefficient (the linear and third-order nonlinear) for transition between two lower-lying electronic levels in the asymmetric parabolic \({\text{GaAs/ Ga}}_{{ 1 {\text{ - x}}}} {\text{Al}}_{\text{x}} {\text{As}}\) quantum well. Total absorption coefficient (linear and nonlinear absorption coefficient) for the transitions between any two electronic states was calculated by using density matrix formalism and the perturbation expansion method. Our results show that the effects of intense laser field and the well dimensions on the optical transitions are more pronounced. If well center is changed to be \({\text{L}}_{\text{c}} 0)\), effective well width decreases (increases) and thus we can obtain the red or blue shift in the peak position of the absorption coefficient by changing the intensities of the non-resonant intense laser field as well as dimensions of the well.

Electromagnetically induced transparency in double quantum dot under intense laser and magnetic fields: from Λ to Ξ configuration

We theoretically investigated the effects of non-resonant intense laser and magnetic fields on the optical properties of asymmetric GaAs/AlGaAs double quantum dot related to the occurrence of electromagnetically induced transparency, using compact density-matrix formalism and effective mass approximation. The chosen structure has the advantage to present x-lambda(Λ)-configuration or y-ladder(Ξ)-configuration for EIT occurrence, depending on lasers polarization, at low values of the non-resonant laser, and to change the configuration from Λ to Ξ at the increase of the x-polarized non-resonant laser intensity. We discussed in detail the influences of the control laser field intensity, non-resonant laser strength and polarization, and magnetic field intensity on the absorption coefficient, refraction index and group index. It is found that: (i) the control laser or the non-resonant laser at the same control laser intensity influences more the system being in x-Ξ-configuration than in x-Λ-configuration and have intermediate effects on y-Ξ-configuration; (ii) the magnetic field has the greatest influence on the system being in x-Λ-configuration and the lowest for y-Ξ-configuration; (iii) the increment of the non-resonant intense laser or magnetic fields induces a red-shift of the transparency windows and sub (super) luminal frequency intervals for the Λ-configuration but a blue-shift for both Ξ-configurations.

Intense laser field effects on the intersubband optical absorption and refractive index change in the [formula omitted]-doped GaAs quantum wells

In this paper, we have investigated the effects of the non-resonant intense laser field on the electronic and optical properties such as linear, nonlinear and the total optical absorption coefficient and refractive index change for transitions between two lower-lying electronic states in the GaAs-based δ-doped quantum well. Within the effective mass approximation, we calculated the eigenvalues and corresponding eigenfunctions as a function of the intense laser parameter by solving the Schrödinger equation in the laser-dressed confinement potential. The analytical expressions of the linear and third-order non-linear optical absorption coefficients and refractive index changes are obtained by using the compact-density matrix formalism. The obtained results show that the separation between ground and first excited energy levels in the δ-doped quantum well decreases in energy by the increase of the laser field intensity and this effect leads to an optical red-shift in the intersubband transitions. This behavior gives us a new degree of freedom in tunability of different device applications based on the optical transitions.