The effect of hydrostatic pressure,temperature and magnetic field on the nonlinear optical properties of asymmetrical Gaussian potential quantum wells

In this study, simultaneous effects of hydrostatic pressure, temperature and magnetic field on the linear and nonlinear intersubband optical absorption coefficients (OACs) and refractive index changes (RICs) in asymmetrical Gaussian potential quantum wells (QWs) are theoretically investigated within the framework of the compact-density-matrix approach and iterative method. The energy eigenvalues and their corresponding eigenfunctions of the system are calculated with the differential method. Our results show that the position and the magnitude of the resonant peaks of the nonlinear OACs and RICs depend strongly on the hydrostatic pressure, temperature and external magnetic field. This gives a new degree of freedom in various device applications based on the intersubband transitions of electrons.     

Combined effects of hydrostatic pressure and temperature on nonlinear properties of an exciton in a spherical quantum dot under the applied electric field

Within the framework of the effective-mass approximation, we have calculated the combined effects of hydrostatic pressure, temperature and applied electric field on an exciton confined in a typical GaAs/Ga_0.7Al_0.3As quantum dot. Several inputs of the confinement potential, hydrostatic pressure, temperature, and applied electric field have been considered. Our findings suggest that (1) the effect of the confinement strength is dominant over the electric field effect, (2) the oscillator strength is an increasing function of the hydrostatic pressure, (3) the absorption coefficients and energy difference depend strongly on the hydrostatic pressure but weakly on the temperature, (4) the absorption coefficients with considering excitonic effects are stronger than those without considering excitonic effects and the absorption peak will move to the right side induced by the electron-hole interaction, (5) the applied electric field may effect either the size or the position of absorption peaks of excitons.     

Pressure and temperature effects on the third-order nonlinear optical properties in GaAs quantum dots

This work is used in the density matrix formalism and the effective mass approximation to study the third harmonic generation coefficient in a GaAs disc-shaped quantum dot with parabolic confinement potential. It is discussed the strong and weak confinement regime. The results show that the third harmonic generation coefficient is strongly dependent on the excitonic pair localization. The study is extended to consider effects such as hydrostatic pressure and temperature to show that it is possible to induce a blue-shift and/or red-shift on the resonant peaks of the third harmonic generation coefficient.     

Electric field effect on the second-order nonlinear optical properties in semiparabolic quantum wells

Electric field effect on the second-order nonlinear optical properties in semiparabolic quantum wells are studied theoretically. Both the second-harmonic generation susceptibility and nonlinear optical rectification depend dramatically on the direction and the strength of the electric field. Numerical results show that both the second-harmonic generation susceptibility and nonlinear optical rectification are always weakened as the electric field increases where the direction of the electric field is along the growth direction of the quantum wells, which is in contrast to the conventional case. However, the second-harmonic generation susceptibility is weakened, but the nonlinear optical rectification is strengthened as the electric field increases where the direction of the electric field is against the growth direction of the quantum wells. Also it is the blue (or red) shift of the resonance that is induced by increasing of the electric field when the direction of the electric field is along (or against) the growth direction of the quantum wells. Finally, the resonant peak and its corresponding to the resonant energy are also taken into account.     

The hydrostatic pressure and temperature effects on Raman scattering of a hydrogenic impurity in a disc-shaped quantum dot

Using the perturbation method and the effective-mass approximation, we studied the combined effects of hydrostatic pressure and temperature on Raman scattering in a disc-shaped quantum dot with a parabolic potential in the presence of an electric field. The differential cross-section involved in this process is calculated. Numerical calculations on a typical GaAs quantum dot are performed. The results show that not only the impurity but also the temperature and the hydrostatic pressure have an influence on the differential cross-section of the system.     

Photoionization and binding energy of a donor impurity in a quantum dot under an electric field: Effects of the hydrostatic pressure and temperature

Using the perturbation approach, we have calculated the donor impurity related photoionization cross-section in a quantum dot under different temperature and hydrostatic pressure conditions. Our calculation have revealed the dependence of the photoionization cross-section on the confinement strength, temperature and hydrostatic pressure.     

Donor impurity states in coupled quantum well wires under hydrostatic pressure and applied electric field

In this work we study the binding energy of the ground state for a hydrogenic donor impurity in laterally coupled GaAs/Ga_1−xAl_xAs quantum well wires, considering the simultaneous effects of hydrostatic pressure and applied electric field. We have used a variational method and the effective mass and parabolic band approximations. The low dimensional structure consists of two quantum well wires with rectangular transverse section coupled by a central Ga_1−xAl_xAs barrier. Our results are reported for several sizes of the structure and we have taken into account variations of the impurity position along the growth direction of the heterostructure.     

Hydrostatic pressure effects on impurity states in GaAs/AlAs quantum wells

Within the framework of effective-mass approximation, we have studied the effects of hydrostatic pressure on the binding energy of a shallow donor impurity in an infinite quantum well by means of a variational method. It is found that the first derivative of the binding energy and energy shift is reliable parameter for describing the structure.     

Linear and nonlinear intersubband optical absorption and refractive index change in asymmetrical semi-exponential quantum wells

Linear and nonlinear intersubband optical absorption and refractive index change in asymmetrical semi-exponential quantum wells are theoretically investigated within the framework of the compact–density–matrix approach and iterative method. The wave functions are obtained by using the effective mass approximation. The energy levels are obtained by numerical method. It is found that the optical absorption coefficients and refractive index changes are strongly affected not only by σ   and _U0$U_0$, but also by the incident optical intensity.     

Simultaneous effects of hydrostatic pressure and applied electric field on the impurity-related self-polarization in GaAs/Ga1−xAlxAs multiple quantum wells

A detailed theoretical study of the combined effects of hydrostatic pressure and in-growth direction applied electric field on the binding energy and self-polarization of a donor impurity in a system of GaAs-(Ga,Al)As coupled square quantum wells is presented. The study is performed in the framework of the effective mass and parabolic band approximations and using a variational procedure. The electron effective mass, the dielectric constant, the barrier height, the well sizes, all them varying with the hydrostatic pressure are taken into account within the study. The results obtained show that the impurity binding energy and its self-polarization bear strong dependencies with the hydrostatic pressure, the strength of the applied electric field, the width of the confining potential barriers, and the impurity position.     

Linear and nonlinear optical properties in a disk-shaped quantum dot with a parabolic potential plus a hyperbolic potential in a static magnetic field

Linear and nonlinear optical properties in a disk-shaped quantum dot (DSQD) with a parabolic potential plus a hyperbolic potential in a static magnetic field are theoretically investigated within the framework of the compact-density-matrix approach and iterative method. The energy levels and the wave functions of an electron are obtained by three kinds of approximation methods. It is found that optical absorption coefficients and refractive index changes are not only by the characteristic parameters of the hyperbolic potential and the confinement frequency, but also by the magnetic field.     

External electric field and hydrostatic pressure effects on the binding energy and self-polarization of an off-center hydrogenic impurity confined in a GaAs/AlGaAs square quantum well wire

Based on the effective-mass approximation within a variational scheme, binding energy and self-polarization of hydrogenic impurity confined in a finite confining potential square quantum well wire, under the action of external electric field and hydrostatic pressure, are investigated. The binding energy and self-polarization are computed as functions of the well width, impurity position, electric field, and hydrostatic pressure. Our results show that the external electric field and hydrostatic pressure as well as the well width and impurity position have a great influence on the binding energy and self-polarization.     

Measurements of sensitivity to hydrostatic pressure and temperature in highly birefringent photonic crystal fibers

We report on experimental studies of polarimetric sensitivity to hydrostatic pressure and temperature in two highly birefringent index guided photonic crystal fibers, in which birefringence is induced by one row of the cladding holes with diameters smaller than the other cladding holes. The sensitivity measurements were carried out in the spectral range from 0.6 μm to 1.6 μm. Our results show that absolute value of the polarimetric sensitivity to hydrostatic pressure can reach 23 rad/MPa × m, which is almost one order of magnitude higher than in conventional fibers with elliptical core. Simultaneously, polarimetric sensitivity to temperature is at least two orders of magnitude lower than in conventional highly birefringent fibers. Moreover, we proved experimentally that one of the investigated fibers is completely insensitive to temperature at certain wavelength.     

Polaron effects on the optical refractive index changes in asymmetrical quantum wells

The optical refractive index changes considering polaron effects in asymmetrical quantum wells are theoretically studied. It is shown that a pronounced optical refractive index changes dependence of the quantum well parameters can be obtained. Moreover, the theoretical values of the optical refractive index changes obviously increase when considering the electron-LO-phonon interaction.     

Simultaneous effects of hydrostatic pressure and temperature on the binding energy of hydrogenic impurity in cylindrical quantum well wires

The effect of hydrostatic pressure and temperature on the ground state binding energy of hydrogenic impurities is investigated in a GaAs/Ga_0.7Al_0.3As cylindrical quantum well wire as a function of the wire radius. The calculations are performed using a variational procedure within the effective mass approximation for a finite confinement potential for various values of the hydrostatic pressure and temperatures. The results are compared with the available data in literature and found to be in a good agreement with them.     

Electric field effects on the linear and nonlinear intersubband optical properties of double semi-parabolic quantum wells

In this work, the effects of the electric field on the optical properties of the symmetric and asymmetric double semi-parabolic quantum wells (DSPQWs) are investigated numerically for typical GaAs/Al_xGa_1−xAs. Optical properties are obtained using the compact density matrix approach. Our calculations for the asymmetric DSPQW show that the resonant peak values of the total refractive index change and total optical absorption coefficient are maximum for a certain value of the applied electric field, due to the anti-crossing effect. However, for the symmetric DSPQW, the resonant peak values of these optical properties decrease monotonically with increasing the applied electric field. Also, our results indicate that a larger value of the optical rectification coefficient of the symmetric DSPQW can be induced by applying a small electric field.     

Impact of Al interdiffusion on optical properties in GaSb/AlGaSb multiple quantum wells

We have studied the effect of the Al interdiffusion on the electronic states of AlGaSb–GaSb quantum wells. Measuring the interdiffusion lengths by means of highly depth-resolved secondary ion mass spectrometry we find that the effect of Al diffusion results in the transformation of the ternary–binary system in a ternary–ternary structure. The modified energy levels, calculated on the basis of the measured chemical profile using a Pösch–Teller potential, are consistent with the blue shifts of the PL peaks measured in samples grown with increasing growth temperature.     

The effect of hydrostatic pressure on subband structure and optical transitions in modulation-doped quantum well

Within the framework of effective-mass approximation, we have calculated theoretically the effects of hydrostatic pressure and doping concentration on subband structure and optical transitions in modulation-doped GaAs/Al_xGa_1−xAs quantum well for different well widths. The electronic structure of modulation-doped quantum well under the hydrostatic pressure is determined by solving the Schrödinger and Poisson equations self-consistently. The results obtained show that intersubband transitions and the subband energy levels in the modulation-doped quantum well can be significantly modified and controlled by the well width, donor concentration and hydrostatic pressure.