Optical Rectification Coefficient Research Articles

Comparison of asymmetric double parabolic-inversed parabolic quantum wells for linear optical (1–2) transition

In present study, for asymmetric double parabolic quantum well (ADPQW) and asymmetric double inverse parabolic quantum well (ADIPQW) the linear optical absorption (OA) coefficient, the linear refractive index change (RIC), resonant peaks of the linear OA and the optical rectification (OR) coefficients are examined as dependent on the structural parameters (barrier width (b) and Al concentration at the well center (σ)). The results display that the variation of all OA and OR coefficients and RIC depend on b and σ-parameter. I have also shown that the σ-parameter has a significant effect on the electronic and optical properties of ADPQW and ADIPQW, and that the energy levels and the dipole moment matrix elements vary depending on the shape of the limiting potential. The intersubband absorption spectrum in the ADPQW shows the blue shift by increasing the b and σ values. Whereas the absorption spectrum for ADIPQW shows blue shift for σ=1 with increasing b-values, this spectrum shows red shifts for σ=5. The electro-optic properties of these structures promise many potential applications in high speed spatial light modulators and switches. So, it can be adjusted RIC and the resonant peak size of the linear OA and OR coefficient by changing Al density at the well center in addition to the barrier dimensions.

Laser-induced nonlinear optical rectification in a two-dimensional quantum pseudodot system

In this work, the effects of intense laser field on the nonlinear optical rectification in a two-dimensional quantum pseudodot system subjected to an uniform external magnetic field have been investigated theoretically. The non-resonant monochromatic intense laser field with circular polarization has been taken into account within the framework of high-frequency Floquet theory. Analytical expression for the coefficient of nonlinear optical rectification is deduced by using the compact-density matrix approach and iterative method. Numerical results show that the nonlinear optical rectification coefficient depends strongly on the magnitude of magnetic field, the chemical potential and zero point of the pseudoharmonic potential. Moreover, we have demonstrated that the strength of intense laser field alters the structure of confinement potential and affects remarkably the nonlinear optical rectification coefficients.

Non-linear optical response of an impurity in a cylindrical quantum dot under the action of a magnetic field

The linear and nonlinear optical response in a cylindrical quantum dot (CQD) of GaAs/Ga0.6Al0.4As with a donor impurity in a uniform magnetic field applied in the axial direction of the cylinder is studied theoretically. The calculations were carried out in approximations of effective mass and two-level quantum systems. Using the variational method, the binding energies and the wave functions of the 1s-like y 2pz-like states for different positions of the impurity inside the CQD were found. It was found that the binding energy is greatest in the center of the CQD and diminishes as the impurity moves radially and/or axially. The optical rectification, the change in the refractive index, and the optical absorption were studied as functions of the energy of a photon incident on the CQD and different intensities of the magnetic field, with an impurity located at various positions. It was found that in a CDQ with an impurity inside, the effect of the variation of the intensity of the magnetic field on the optical response is much less than the effect produced by the variation of the position of the impurity. The physical reason for this behavior is that in nanostructures with impurities the Coulomb confinement is stronger than the magnetic confinement. It was also found that when the impurity is in the center of the quantum dot, the optical rectification coefficient is zero, due to the symmetry that the wave function of the impurity exhibits at this geometric point. When the impurity moves in the axial direction, the symmetry is broken and the optical rectification coefficient is different from zero, and its value increases as the impurity moves away from the center of the CQD.

Effects of electromagnetic fields on the nonlinear optical properties of asymmetric double quantum well under intense laser field

In this study, the effects of electric and magnetic fields on the optical rectification and second and third harmonic generation in asymmetric double quantum well under the intense non-resonant laser field is theoretically investigated. We calculate the optical rectification and second and third harmonic generation within the compact density-matrix approach. The theoretical findings show that the influence of electric, magnetic, and intense laser fields leads to significant changes in the coefficients of nonlinear optical rectification, second and third harmonic generation.

Donor Impurity States in Semiconductor Zincblende Nitride Quantum Systems as a Source of Nonlinear Optical Response.

The optical absorption and the optical rectification coefficients associated to hydrogenic impurity interstate transitions in zincblende GaN-based nanostructures of the quantum wire type are investigated. The system is assumed to have cylindrical shape and the influence of external tuning probes such as hydrostatic pressure and static electric fields is particularly taken into account. The electron states are obtained within the effective mass approximation, via the exact diagonalization of the donor-impurity Hamiltonian with parabolic confinement. The nonlinear optical coefficients are calculated using a nonperturbative solution of the density-matrix Bloch equation. Our results show that the resonance-related features of the optical response become shifted in the frequency range of the incident radiation due to the effect of the hydrostatic pressure, the strength of the applied field and the change in the impurity center position.

Effects of applied electric and magnetic fields on the nonlinear optical rectification and second-harmonic generation in a graded quantum well under intense laser field

In this present study, the effects of electric and magnetic fields on the nonlinear optical rectification and second-harmonic generation in a graded quantum well under intense laser field have been investigated theoretically. The energy eigenvalues and their corresponding eigenfunctions are obtained by solving Schrodinger equation within the framework of effective mass approximation. The analytic expressions for the optical properties are calculated by the compact-density-matrix approach and iterative method. The numerical results are presented for a typical GaAs/Ga1−xAlxAs quantum well. The results show that the nonlinear optical rectification and second-harmonic generation coefficients are considerably affected by the electromagnetic fields and intense laser field.

Polaron effect on the optical rectification in spherical quantum dots with electric field**Project supported by the National Natural Science Foundation of China (Grant No. 11364028), the Major Projects of the Natural Science Foundation of Inner Mongolia Autonomous Region, China (Grant No. 2013ZD02), and the Project of “Prairie Excellent” Engineering in Inner Mongolia Autonomous Region, China.

The polaron effect on the optical rectification in spherical quantum dots with a shallow hydrogenic impurity in the presence of electric field is theoretically investigated by taking into account the interactions of the electrons with both confined and surface optical phonons. Besides, the interaction between impurity and phonons is also considered. Numerical calculations are presented for typical Zn1−xCdxSe/ZnSe material. It is found that the polaronic effect or electric field leads to the redshifted resonant peaks of the optical rectification coefficients. It is also found that the peak values of the optical rectification coefficients with the polaronic effect are larger than without the polaronic effect, especially for smaller Cd concentrations or stronger electric field.

Hydrogenic impurity, external electric and magnetic fields effects on the nonlinear optical properties of a multi-layer spherical quantum dot

In this work, effects of an on-center hydrogenic impurity, external electric and magnetic fields on the optical rectification coefficient (ORC), second and third harmonic generations (SHG and THG) of a multi-layer spherical quantum dot (MLSQD) are studied. Energy eigenvalues and eigenvectors are calculated using the direct matrix diagonalization method and optical properties are obtained using the compact density matrix approach. Our results reveal that the hydrogenic impurity and external fields have a great influence on these optical quantities. Hydrogenic impurity reduces the magnitude of the resonant peaks and shifts them to the higher energies. An increase in the magnetic (electric) field, leads to increase (decrease) the interval energies and the dipole moment matrix elements. Therefore, resonant peaks of these optical quantities find an obvious blue (red) shift and their magnitudes enhance (diminish) with increasing the external magnetic (electric) field.

Tailoring nonlinear optical rectification coefficient of impurity doped quantum dots by invoking Gaussian white noise

We make a rigorous exploration of profiles of nonlinear optical rectification (NOR) coefficient of impurity doped quantum dots (QDs) in presence and absence of noise. We have exploited Gaussian white noise in the present study. The quantum dot is doped with Gaussian impurity. Noise has been introduced to the system additively and multiplicatively. A perpendicular magnetic field serves as a confinement source and a static external electric field has been applied. The NOR profiles have been monitored as a function of incident photon energy when several important parameters such as electric field strength, magnetic field strength, confinement energy, dopant location, relaxation time, Al concentration, dopant potential, and noise strength assume different values. In addition, the role of mode of application of noise (additive/multiplicative) on the NOR profiles has also been examined thoroughly. The NOR profiles are found to be endowed with interesting observations such as shift of peak position and maximization/minimization of peak intensity. However, presence of noise prominently alters the features of NOR profiles through some interesting manifestations and often induces one photon resonance enhancement. Furthermore, the mode of application of noise (additive/multiplicative) also controls the NOR profiles in disparate as well as often contrasting manners. The observations indicate possibilities of tailoring the NOR coefficient of doped QD systems in presence of noise which bears tremendous technological importance.

Nonlinear optical rectification in a vertically coupled lens-shaped InAs/GaAs quantum dots with wetting layers under hydrostatic pressure and temperature

In this paper we explore the structure parameters, hydrostatic pressure and temperature effects on Nonlinear optical rectification (NOR) in an asymmetric vertically coupled lens-shaped InAs/GaAs quantum dots.During epitaxial growth, lens-shaped quantum dots (QDs) are formed on the wetting layer (WL). Many theoretical works have neglected WL and its effect on nonlinear optical properties of QD-based systems for sake of simplicity. However, in this work the WL has been shown to be so influential in the intersubband energy and nonlinear optical rectification magnitude. Also, a detailed and comprehensive study of the nonlinear optical rectification is theoretical investigated within the framework of the compact density-matrix approach and finite difference method (FDM).It's found that nonlinear optical rectification coefficient is strongly affected not only by the WL, but also by the pressure, temperature and the coupled width between the QDs.Obtained results revealed that a red or a blue shift cane be observed. This behavior in the NOR gives a new degree of freedom in regions of interest for device applications.

Optical properties of a semispherical quantum dot placed at the center of a cubic quantum box: Optical rectification, second and third-harmonic generations

In the present paper, we first apply finite element method (FEM) and Arnoldi algorithm to obtain energy eigenvalues and eigenfuctions of a semispherical quantum dot located at the center of a cubic box. Then, the compact-density matrix approach and an iterative method are used to find the optical rectification (OR) coefficient, second harmonic generation (SHG) and third harmonic generation (THG). Numerical calculations are performed for the typical GaAs/Ga1−xAlxAs system. It is found that OR coefficient has a red-shift when the semispherical radius R becomes larger. Raising R and potential height V0, the magnitude of OR coefficient, SHG and THG are increased. Moreover, the position of resonant peaks of OR coefficient, SHG and THG are affected by the semispherical radius and potential height.

Influence of applied electric fields on the electron-related second and third-order nonlinear optical responses in two dimensional elliptic quantum dots

The coefficients of the second-order nonlinear optical rectification and the generation of second and third harmonics, related to electron energy transitions in a two-dimensional elliptical quantum dot are calculated. The conduction band states are obtained using the finite element method to numerically solve the effective mass Schrödinger differential equation in the parabolic approximation, including the influence of an externally applied static electric field. It comes about that the geometry of the ellipse has a strong influence on the optical response, being the large eccentricity case the more favorable one. Furthermore, it is shown that the application of an electric field is of most importance for achieving well-resolved higher harmonics signals.

Resonant peaks of the linear optical absorption and rectification coefficients in GaAs/GaAlAs quantum well: Combined effects of intense laser, electric and magnetic fields

In this study, the resonant peaks of the linear optical absorption (OA) and rectification coefficients in GaAs/GaAlAs quantum well are calculated as dependent on the applied electric field (F), the magnetic field (B) and the laser field intensity parameter (α0). Our results show that the shape of confined potential profile, the energy levels and the dipole moment matrix elements are changed as dependent on the F, B and α0. Also, the resonant peaks of the OA and rectification coefficients depend on the applied external field effects. Therefore, the variation of the resonant peaks of these coefficients which can be appropriate for various optical modulators and infrared optical device applications can be smoothly obtained by the alteration electric, magnetic and intense laser field.

Nonlinear refractive index change and optical rectification in a GaN-based step quantum wells with strong built-in electric field

Based on the compact density matrix approach, the linear and nonlinear refractive index change (RIC) and optical rectification (OR) coefficients in a GaN -based step QW with strong built-in electric field (BEF) have been theoretically deduced and investigated in detail. The analytical electronic state is derived by the two airy functions. And the band nonparabolicity is taken into account by using an energy dependence effective mass (EDEM) method. Numerical calculations on a four-layer AlN / GaN / Al x Ga 1-x N / AlN step QW are performed, and the curves for the geometric factors, the linear, the nonlinear, the total RICs and the OR coefficients as functions of the structural parameters of the step QW are discussed. The features for these curves were specified and reasons for the features were explained reasonably. It is found that the decreasing of well width Lw, and step barrier width Lb and the doped concentration x in step barrier will result in the significant enhancement of the RICs. With the decrease of Lw, Lb and x, the resonant photon energies of RIC and OR coefficients have obvious blue-shift. Moreover, the RIC and OR coefficients behave different dependence on the structural parameters of the GaN -based step QWs. The profound physical reasons are also analyzed.

Nonlinear optical rectification of hydrogenic impurity in a disk-like parabolic quantum dot: The role of applied magnetic field

We report a detailed theoretical study of the effect of combined electric and magnetic field on the nonlinear optical rectification of a hydrogenic impurity, confined in a two dimensional disk-like quantum dot, with parabolic confinement potential. We use the compact density matrix formalism and iterative method to obtain nonlinear optical rectification and absorption coefficients. To find energy levels and wave functions, we employ exact diagonalization method in the effective mass approximation. As main result, we found that the transition energy from ground to first excited state redshifts with increasing the magnetic field while blueshifts for transition from ground to second excited state, moreover, for former transition, nonlinear optical rectification coefficient decreases with increasing magnetic field in contrast to that occurs for latter one.

Nonlinear optical rectification and second-harmonic generation in a semi-parabolic quantum well under intense laser field: Effects of electric and magnetic fields

The effects of electric and magnetic fields on the nonlinear optical rectification and second harmonic generation coefficients related with intersubband transitions in a semi-parabolic quantum well under intense laser field are theoretically studied. The energy levels and corresponding wave functions are obtained by solving the conduction band Schrödinger-like equation in the parabolic approximation and the envelope function approach. Numerical calculations are presented for a typical GaAs/Ga1-xAlxAs quantum well. The results show that both the non-resonant intense laser field and the static external fields have significant influences on the magnitude and resonant peak energy positions of the coefficients under study.

Electric field-induced nonlinear optical properties of a hydrogenic impurity in a GaAs/GaAlAs quantum dot: effects of spin–orbit interactions

Nonlinear optical properties, optical rectification coefficients and the second-order and third-order harmonic generation coefficients as a function of photon energy are dealt in a GaAs/Ga0.8Al0.2As quantum dot in the presence of electric field and the spin–orbit interactions. The Dresselhaus and the Rashba spin–orbit interactions are added in the Hamiltonian. The electric field-induced photoionization cross section with the normalized photon energy for an on-centre donor impurity in the quantum dot is studied. The effect of nonparabolicity is included in the Hamiltonian. The spin–orbit interaction as a function of photon energy is investigated. The computations are carried out within the framework of the single band effective mass approximation using variational technique and the compact density approach. It is found that the spin–orbit interaction coefficients show strong effects on the resonant position of harmonic generations. The results are compared with the recent investigations.

MAGNETIC FIELD, PRESSURE AND TEMPERATURE DEPENDENT OPTICAL PROPERTIES IN A GaAs 9.0 P 1.0 QUANTUM DOT

Simultaneous effects of magnetic field, pressure and temperature on the exciton binding energies are found in a 9.0 1.0 6.0 4.0 GaAs P / GaAs P quantum dot. Numerical calculations are carried out taking into consideration of spatial confinement effect. The cylindrical system is taken in the present problem with the strain effects. The electronic properties and the optical properties are found with the combined effects of magnetic field strength, hydrostatic pressure and temperature values. The exciton binding energies and the nonlinear optical properties are carried out taking into consideration of geometrical confinement and the external perturbations.Compact density approach is employed to obtain the nonlinear optical properties. The optical rectification coefficient is obtained with the photon energy in the presence of pressure, temperature and external magnetic field strength. Pressure and temperature dependence on nonlinear optical susceptibilities of generation of second and third order harmonics as a function of incident photon energy are brought out in the influence of magnetic field strength. The result shows that the electronic and nonlinear optical properties are significantly modified by the applications of external perturbations in a 9.0 1.0 6.0 4.0 GaAs P / GaAs P quantum dot.

Optical rectification and third harmonic generation of spherical quantum dots: Controlling via external factors

In this paper simultaneous effects of pressure, temperature, external electric field and laser radiation on the optical rectification and third harmonic generation of a spherical quantum dot with parabolic confinement and dressed impurity are studied. By means of matrix diagonalization technique, energy eigenvalues and functions are evaluated and used to find the optical rectification coefficient and third harmonic generation of the system via density operator method. It is shown that these nonlinear optical quantities strongly depend on pressure, temperature, electric field, confinement frequency and dressing laser intensity. Obvious effects of these external factors propose new facilities with different effects to control nonlinear optical properties of such systems.

Effects of temperature on binding energy and the nonlinear optical properties of a hydrogenic donor in a GaAs/Ga0.8Al0.2As pillbox immersed in a Ga0.6Al0.4As material

Effect of temperature on the hydrogenic donor binding energy is found in a GaAs/Ga0.8Al0.2As pillbox surrounded by Ga0.6Al0.4As for various lengths of the pillbox and the barrier thicknesses. Photoionization cross section as a function of normalized photon energy, for various values of temperatures, is computed. Some nonlinear optical properties as a function of photon energy are dealt for a fixed length of the pillbox. Optical rectification coefficients, second order and the third order harmonic generation coefficients are found as a function of photon energy for various values of temperatures. It is shown that the optical rectification and second order and the third order harmonic generation coefficients are quite sensitive to the effect of temperature. It is also observed that the electronic properties and the nonlinear optical properties have more influence on the temperature and the geometrical confinement. The results are in good agreement with the recent investigations.