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In this paper, we calculated the electronic and optical absorption coefficient of the Manning-like double quantum well under the external applied electric and magnetic fields. To calculate the linear and third-order nonlinear optical absorption coefficients is used two-level approach in the density matrix expansion. The findings show that the electronic structure can be adjusted by changing the well and barrier widths, the well depth, the coupling between the wells as well as applied external field intensities. In addition, direct and indirect exciton states in asymmetric double quantum wells with Manning-like potential under electric field are compared with experimental studies. From the obtained results, it is concluded that the Manning-like potential is an excellent strategy for modeling electronic states in asymmetric double quantum wells with steep potential barriers and also the Manning-like potential allows modeling interdiffusion effects at the interfaces of multiple heterostructures.

© 2021 Elsevier LtdIn this work, we perform a theoretical investigation on the effect of position-dependent effective mass on binding energy and optical absorption coefficient for donor impurities in single and double quantum wells defined by Konwent potential. We have used the diagonalization method by choosing a wave function based on the trigonometric orthonormal base functions that are solutions of an infinite square quantum well to get the energy spectrum of the system, the variational method for impurity binding energy is used and also linear absorption coefficient is deduced from the density matrix approach and perturbation expansion method. Numerical results reveal that impurity binding energy as well as the linear optical absorption coefficient are remarkably affected by the confinement potential parameters, position of an impurity and the approach used for the effective electron mass. Moreover, it is seen that with an appropriate choice of the structure parameters and position dependence effective mass distribution, the optical response of the system can be tailored in a controllable manner.

Using the effective mass and parabolic band approximations, we investigated the position-dependent effective mass and non-resonant intense laser field effects on the first and third-order corrections of the absorption and relative changes of the refraction index coefficients for intersubband transition in Razavy-like quantum wells. Calculations have been extended to the spherical Razavy-like quantum dots electronic structure. We have shown that depending on the combinations of the Razavy-like potential parameters, the quantum wells can evolve from parabolic confinement in an isolated quantum well to a configuration of two coupled quantum wells. We have shown that in general the transition energies (dipole matrix elements) between the ground state and the first excited state: i) are decreasing (increasing) functions of M-parameter, ii) are increasing (decreasing) functions of A-parameter, iii) they increase (decrease) when considering the position-dependent effective mass effects, and iv) are increasing (decreasing) functions of the intense laser field parameter. In the case of the optical absorption and relative changes in the refractive index coefficients, we have shown blueshifts or redshifts by changing the A-, M-, and α0-parameters and by considering the effects of the position-dependent effective mass. In spherical quantum dots, we have shown that with an appropriate value of A- and M-parameters the system can evolve from a spherical quantum dot with infinite parabolic potential.

WOS: 000462810600047, In the present paper, we theoretically investigate the effect of applied external fields, such as electric, magnetic, and intense terahertz laser fields on the optical absorption and the relative refractive index change coefficients of triple delta-doped quantum well structures. To investigate the applied external field effects, we perform the calculation of the allowed subband energy levels and their corresponding eigen-functions using the diagonalization method within the framework of the effective-mass approximation. The effects of the applied external fields on the nonlinear optical properties of the quantum well structure are treated within the compact-density-matrix approach via the iterative method. The numerical results obtained are presented for two different values of electric, magnetic, and intense terahertz laser fields. These results show that changing the intensity of the external electric, magnetic, and intense terahertz laser field. It is concluded that the nonlinear optical response of the triple delta-doped structure can be significantly changed through the changes in the configuration of the external probes.

WOS: 000453499500082, 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 Schordinger 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 spectrurn., CODI-Universidad de Antioquia (Estrategia de Sostenibilidad de la Universidad de Antioquia); CODI-Universidad de Antioquia (project : "Efectos opticos intersubbanda, no lineales de segundo orden y dispersion Raman, en sistemas asimetricos de pozos cuanticos acoplados"); CODI-Universidad de Antioquia (project: "Efectos de capas delta dopadas en pozos cuanticos como fotodetectores en el infrarrojo"); Facultad de Ciencias Exactas y Naturales-Universidad de Antioquia (CAD exclusive dedication project 2018-2019); Universidad EIA; Universidad de Antioquia; Facultad de Ciencias Exactas y Naturales-Universidad de Antioquia (ALM exclusive dedication project 2018-2019), This research was partially supported by Colombian Agencies: CODI-Universidad de Antioquia (Estrategia de Sostenibilidad de la Universidad de Antioquia and projects: "Efectos opticos intersubbanda, no lineales de segundo orden y dispersion Raman, en sistemas asimetricos de pozos cuanticos acoplados" and "Efectos de capas delta dopadas en pozos cuanticos como fotodetectores en el infrarrojo") and Facultad de Ciencias Exactas y Naturales-Universidad de Antioquia (CAD exclusive dedication project 2018-2019 and ALM exclusive dedication project 2018-2019). The authors are grateful to the Universidad EIA and Universidad de Antioquia for its financial support through the EIA-UdeA-UdeM-project "Generacion de segundo armonico, rectificacion optica y dispersion Raman entre estados electronicos en pozos cuanticos acoplados". RLR and JPGP are grateful to Semillero de Investigacion Universidad EIA "Nanoestructuras Semiconductoras".

WOS: 000449621100040, 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.

Within the structure of parabolic band and effective-mass approximations, the effects of magnetic and intense terahertz laser fields on the donor impurity-associated photoionization cross-section and nonlinear optical properties in delta-doped quantum well wires are studied using the variational method. The binding energy and photoionization cross-section as functions of doping concentrations, magnetic and terahertz laser fields are computed. The linear, third-order nonlinear and the corresponding total absorption coefficients and relative refractive index changes with a function of incoming photon energy for various doping concentrations, magnitude of terahertz laser and magnetic fields are investigated. The numerical results bring out that the donor impurity binding energy, photoionization cross-section, and nonlinear optical properties in the structure are strongly dependent on doping concentrations. In addition, it has been observed that the magnetic and intense terahertz laser fields cause considerable changes in the binding energy, photoionization cross section and nonlinear spectral properties of the system.

This article reports a theoretical study of the intersubband optical properties in quantum wells with modified Manning potential considering the effects of position-dependent effective mass. Calculations are made in the effective mass and parabolic band approximations. The electronic spectrum, dipole matrix element for intersubband transitions, optical absorption coefficient, and refractive index coefficient are reported. Modifying the Manning potential’s three parameters is a useful tool to simulate single and multiple quantum wells. The solution of the eigenvalues differential equation is implemented through the expansion technique based on orthonormal trigonometric functions. Such a procedure is contrasted with those obtained from solving the problem by using the finite element method. Both methods of solving the differential equations report results with excellent agreement between them and the possibility of achieving the desired precision in the spectrum energy and the wave functions and the calculated observable. The results presented here are useful for studying isolated and multiple quantum wells where interdiffusion effects are involved in the interfaces. The findings demonstrate the versatility of the modified Manning potential since, by properly manipulating its three parameters, it is possible to tune the spectrum of energies with potential applications in next-generation optoelectronic devices.

In this paper we are reporting the computation for the Nonlinear Optical Rectification (NOR) and the Second and Third Harmonic Generation (SHG and THG) related with electronic states of asymmetric double Si- δ -doped quantum well in a GaAs matrix when this is subjected to an in-plane ( x -oriented) constant magnetic field effect. The work is performed in the effective mass and parabolic band approximations in order to compute the electronic structure for the system by a diagonalization procedure. The expressions for the nonlinear optical susceptibilities, χ 0 ( 2 ) , χ 2 ω ( 2 ) , and χ 3 ω ( 3 ) , are those arising from the compact matrix density formulation and stand for the NOR, SHG, and THG, respectively. This asymmetric double δ -doped quantum well potential profile actually exhibits nonzero NOR, SHG, and THG responses which can be easily controlled by the in-plane ( x -direction) externally applied magnetic field. In particular we find that for the chosen configuration the harmonic generation is in the far-infrared/THz region, thus and becoming suitable building blocks for photodetectors in this range of the electromagnetic spectra.

WOS: 000411546800020, The effects of electric and magnetic fields on the second and third harmonic generation coefficients in a Morse potential quantum well are theoretically studied. The energy levels and corresponding wave functions are obtained by solving the Schrodinger equation for the electron in the parabolic band scheme and effective mass approximations and the envelope function approach. The results show that both the electric and the magnetic fields have significant influence on the magnitudes and resonant peak energy positions of the second and third harmonic generation responses. In general, the Morse potential profile becomes wider and shallower as gamma-parameter increases and so the energies of the bound states will be functions of this parameter. Therefore, we can conclude that the effects of the electric and magnetic fields can be used to tune and control the optical properties of interest in the range of the infrared electromagnetic spectrum. (C) 2017 Elsevier B.V. All rights reserved., CODI-Universidad de Antioquia (Estrategia de Sostenibilidad de la Universidad de Antioquia); Facultad de Ciencias Exactas y Naturales-Universidad de Antioquia (CAD); Facultad de Ciencias Exactas y Naturales-Universidad de Antioquia (ALM); Universidad EIA; Universidad de Antioquia, This research was partially supported by Colombian Agencies: CODI-Universidad de Antioquia (Estrategia de Sostenibilidad de la Universidad de Antioquia) and Facultad de Ciencias Exactas y Naturales-Universidad de Antioquia (CAD and ALM exclusive dedication project 2016-2017). CAD and RLR are grateful to Universidad EIA and Universidad de Antioquia for financial support through the EIA-UdeA-UdeM-projects "Desarrollo de fotodetectores en el infrarrojo usando pozos cuanticos ajustables con dopamiento delta dentro del pozo".

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 Schrodinger 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.

WOS: 000457429700005, A detailed theoretical study on the electron-related optical responses in triple delta-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 delta-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 delta-doping concentration.

WOS: 000394635200076, In this work we shall present a study of inelastic light scattering involving inter-subband electron transitions in coupled GaAs-(Ga,AI)As quantum wells. Calculations include the electron related Raman differential cross section and Raman gain. The effects of an external nonresonant intense laser field are used in order to tune these output properties. The confined electron states will be described by means of a diagonalization procedure within the effective mass and parabolic band approximations. It is shown that the application of the intense laser field can produce values of the intersubband electron Raman gain above 400 cm(-1). The system proposed here is an alternative choice for the development of Al chi Ga1-chi As semiconductor laser diodes that can be tuned via an external nonresonant intense laser field. (C) 2017 Elsevier B.V. All rights reserved., Colombian Agencies: CODI-; Mexican PRODEP for a Posdoctoral Grant [09/2016-08/2017]; Universidad EIA; Universidad de Antioquia through the EIA-UdeA-UdeM-project "Propiedades Opto-electronicas de sistemas altamente confinados: Una aproximaciOn teorica"; Facultad de Ciencias Exactas y Naturales-Universidad de Antioquia (CAD and ALM-exclusive dedication projects 2016-2017), This research was partially supported by Colombian Agencies: CODI-Universidad de Antioquia (Estrategia de Sostenibilidad de la Universidad de Antioquia and projects: "Propiedades opticas de impurezas, excitones y moleculas en puntos cuanticos autoensamblados" and "On the way to development of new concept of nanostructure-based THz laser") and Facultad de Ciencias Exactas y Naturales-Universidad de Antioquia (CAD and ALM-exclusive dedication projects 2016-2017). AT thanks Mexican PRODEP for a Posdoctoral Grant 09/2016-08/2017. CAD and RLR are grateful to Universidad EIA and Universidad de Antioquia for financial support through the EIA-UdeA-UdeM-project "Propiedades Opto-electronicas de sistemas altamente confinados: Una aproximaciOn teorica".

WOS: 000454472000163, In the present study we have investigated the bound energy levels and intersubband optical transitions in the Tietz-Hua quantum well for a spatially varying effective mass distribution. The energy levels and eigenfunctions are obtained by solving the effective mass equation through a variational approach. The obtained numerical calculations show that the spatially varying effective mass has a significant effect on the subband energies and transitions between the sub bands in the Tietz-Hua quantum well. We conclude that, the energy levels and hence energy differences between the subband states decrease with increasing the stability and uniformity of the effective mass and eventually converge to the results of the constant effective mass. Furthermore, it was found that the size of the Tietz-Hua quantum well has an important effect on optical responses based on the intersubband transitions and additionally, the asymmetrical form of the Tietz-Hua quantum well is more predominant in stable and uniform effective mass case.

In this present work, the effect of non-resonant, mono-chromatic intense laser field (ILF) on the linear and nonlinear optical properties of a semi-exponential quantum well (SEQW) is investigated theoretically within the effective-mass and envelope wave function approach. The bound subband energy levels and their envelope wave functions of the structure are calculated by using the diagonalization method. The optical properties of the system are obtained by using the compact-density matrix approach. The obtained numerical results show that the applied ILF and structure parameters have a significant impact on the optical properties of these structures, such as the linear, third-order nonlinear and total absorption coefficients and relative refractive index changes. Furthermore, from the findings of this study, it has been concluded that the linear and nonlinear optical properties in a SEQW under the ILF can be tuned by changing structure parameters, such as the effective range and depth of the system. © 2019 Elsevier GmbH

WOS: 000465157600059, 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 Schrodinger 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., Colombian Agency: CODI-Universidad de Antioquia (Estrategia de Sostenibilidad de la Universidad de Antioquia); Colombian Agency: CODI-Universidad de Antioquia (project "Efectos de capas delta dopadas en pozos cuanticos como fotodetectores en el infrarrojo"); Colombian Agency: Facultad de Ciencias Exactas y Naturales-Universidad de Antioquia (CAD-exclusive dedication project 2018-2019); Scientific Research Project Fund of Cumhuriyet University (CUBAP) [F-557], This research was partially supported by Colombian Agencies: CODI-Universidad de Antioquia (Estrategia de Sostenibilidad de la Universidad de Antioquia and project "Efectos de capas delta dopadas en pozos cuanticos como fotodetectores en el infrarrojo") and Facultad de Ciencias Exactas y Naturales-Universidad de Antioquia (CAD-exclusive dedication project 2018-2019). This work used resources of the Centro Nacional de Processamento de Alto Desempenho em Sao Paulo (CENAPAD-SP). The authors are grateful to The Scientific Research Project Fund of Cumhuriyet University (CUBAP) under the project number F-557.

WOS: 000425197400031, For a quantum well which has the Tietz-Hua potential, the ground and some excited donor impurity binding energies and the total absorption coefficients, including linear and third order nonlinear terms for the transitions between the related impurity states with respect to the structure parameters and the impurity position as well as the electric field strength are investigated. The binding energies were obtained using the effective-mass approximation within a variational scheme and the optical transitions between any two impurity states were calculated by using the density matrix formalism and the perturbation expansion method. Our results show that the effects of the electric field and the structure parameters on the optical transitions are more pronounced. So we can adjust the red or blue shift in the peak position of the absorption coefficient by changing the strength of the electric field as well as the structure parameters. (C) 2017 Elsevier B.V. All rights reserved., Scientific Research Project Fund of Cumhuriyet University (CUBAP) [F-516]; Scientific Research Project Fund of Cumhuriyet University (CUBAP) [F-516], The authors are grateful to The Scientific Research Project Fund of Cumhuriyet University (CUBAP) under the project number F-516.

The combined effects of electric and magnetic fields on the optical absorption coefficients and refractive index changes related to the intersubband transitions within the conduction band of asymmetric GaAs / Ga 1 - x Al x As double inverse parabolic quantum wells are studied using the effective-mass approximation and the compact density-matrix approach. The results are presented as a function of the incident photon energy for the different values of the electromagnetic fields and the structure parameters such as quantum well width and the Al concentration at the well center. It is found that the optical absorption coefficients and the refractive index changes are strongly affected not only by the magnitudes of the electric and magnetic fields but also by the structure parameters of the system.

WOS: 000357233800004, 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 Schrodinger-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. (C) 2015 Elsevier Ltd. All rights reserved.

WOS: 000451653700009, In the present study, we theoretically reported the effects of applied external fields, such as intense laser field and electric and magnetic fields, on the optical absorption coefficient and refractive index changes in the Tietz-Hua potential quantum well by the compact density-matrix approach. For this, we first calculated the subband energy levels and their corresponding electronic wave functions of the structure by solving the one-dimensional Schrodinger equation within the framework of the effective mass and envelope wave function approximations. Our theoretical results show that the optical absorption coefficient and refractive index changes in the Tietz-Hua potential quantum well are sensitive to the applied external fields. The absorption spectra in the structure can be adjusted depending on the purpose by changing the strength of the applied external fields, and these results can be used to tune and control the electronic and optical properties of the Tietz-Hua potential quantum well., Scientific Research Project Fund of Cumhuriyet University (CUBAP) [TEKNO-019], The authors are grateful to the Scientific Research Project Fund of Cumhuriyet University (CUBAP) under the project number TEKNO-019.

WOS: 000414180500020, In this study, the effects of the electric and magnetic fields as well as structure parameter-gamma on the total absorption coefficient, including linear and third order nonlinear absorption coefficients for the optical transitions between any two subband in the Tietz-Hua quantum well have been investigated. The optical transitions were investigated by using the density matrix formalism and the perturbation expansion method. The Tietz-Hua quantum well becomes narrower (wider) when the gamma - structure parameter increases (decreases) and so the energies of the bound states will be functions of this parameter. Therefore, we can provide the red or blue shift in the peak position of the absorption coefficient by changing the strength of the electric and magnetic fields as well as the structure parameters and these results can be used to adjust and control the optical properties of the Tietz-Hua quantum well., Scientific Research Project Fund of Cumhuriyet University (CUBAP) [F-516], The authors are grateful to The Scientific Research Project Fund of Cumhuriyet University (CUBAP) under the project number F-516.

In this study, the first-order linear, third-order nonlinear, and total absorption coefficients for the intersubband transition between the two lower-lying electronic levels in both symmetric and asymmetric double Morse quantum wells under the non-resonant high-frequency intense laser field are investigated. The study takes into account the effects of the structure parameters. The results show that the electronic and also accordingly optical properties of the structures which we focus on can be adjustable to obtain a convenient response to certain studies or purposes by changing the applied external field and optical intensity as well as structure parameters. © 2019, Facultad de Ciencias Físicas y Matemáticas: 2018-2019 Departamento Administrativo de Ciencia, Tecnología e Innovación: 80740-173-2019 Universidad de Antioquia, This work was supported by Colombian Agencies: CODI-Universidad de Antioquia (Estrategia de Sostenibilidad de la Universidad de Antioquia and projects “Propiedades magneto-ópticas y óptica no lineal en superredes de Grafeno” and “Estudio de propiedades ópticas en sistemas semiconductores de dimensiones nanoscópicas”), and Facultad de Ciencias Exactas y Naturales-Universidad de Antioquia (CAD exclusive dedication project 2018-2019). The authors also acknowledge the financial support from the Colombian Agency El Patrimonio Autónomo Fondo Nacional de Financiamiento para la Ciencia, la Tecnología y la Innovación, Francisco José de Caldas– COLCIENCIAS (project 80740-173-2019 ).

WOS: 000394635200014, In this work, within the effective mass approximation we have performed a theoretical study of electronic states, the intersubband-related optical absorption coefficient and relative refractive index change properties in the GaAs-based double delta-doped quantum well under non-resonant intense laser field. By solving the Schrodinger equation in the laser-dressed confinement potential, We calculated eigenvalues and corresponding eigenfunctions as an intense laser parameter. We concluded that the separation between ground and first excited energy levels in the double delta-doped quantum well increases in energy by the increase of the laser field intensity and this effect leads to an optical blue-shift in intersubband transitions. Therefore a significant tunability of the optical transitions in double delta-doped quantum well can be achieved by modulating the intensity of the intense laser field. (C) 2016 Elsevier B.V. All rights reserved.

WOS: 000400556100048, 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 GaAs/ Ga1-xAlxAs 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 Lc < 0 (L-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., Scientific Research Project Fund of Cumhuriyet University (CUBAP) [F-470], The authors are grateful to The Scientific Research Project Fund of Cumhuriyet University (CUBAP) under the project number F-470.

WOS: 000401386400032, 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 delta-doped GaAs quantum well is theoretically studied by solving the Schrodinger 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.

WOS: 000386644500050, We have calculated the effects of electric and intense laser fields on the binding energies of the ground and some excited states of conduction electrons coupled to shallow donor impurities as well as the total optical absorption coefficient for transitions between 1s and 2p(+/-) electron-impurity states in a asymmetric parabolic GaAs/Ga1-x AlxAs quantum well. The binding energies were obtained using the effective-mass approximation within a variational scheme. Total absorption coefficient (linear and nonlinear absorption coefficient) for the transitions between any two impurity states were calculated from first- and third-order dielectric susceptibilities derived within a perturbation expansion for the density matrix formalism. Our results show that the effects of the electric field, intense laser field, and the impurity location on the binding energy of 1s-impurity state are more pronounced compared with other impurity states. If the well center is changed to be L-c0), the effective well width decreases (increases), and thus we can obtain the red or blue shift in the resonant peak position of the absorption coefficient by changing the intensities of the electric and non-resonant intense laser field as well as dimensions of the well and impurity positions. (C) 2016 Elsevier B.V. All rights reserved., Colombian Agency: Universidad de Antioquia; Colombian Agency: project: "Propiedades opticas de impurezas, excitones y moleculas en puntos cuanticos autoensamblados", Facultad de Ciencias Exactas y Naturales-Universidad de Antioquia (CAD-exclusive dedication project); Colombian Agency: project: "On the way to development of new concept of nanostructure-based THz laser"), Facultad de Ciencias Exactas y Naturales-Universidad de Antioquia (CAD-exclusive dedication project); Colombian Agency: El Patrimonio Autonomo Fondo Nacional de Financiamiento para la Ciencia, la Tecnologia y la Innovacion, Francisco Jose de Caldas, This research was partially supported by Colombian Agencies: Universidad de Antioquia and projects: "Propiedades opticas de impurezas, excitones y moleculas en puntos cuanticos autoensamblados" and "On the way to development of new concept of nanostructure-based THz laser"), Facultad de Ciencias Exactas y Naturales-Universidad de Antioquia (CAD-exclusive dedication project 2015-2016), El Patrimonio Autonomo Fondo Nacional de Financiamiento para la Ciencia, la Tecnologia y la Innovacion, Francisco Jose de Caldas.

WOS: 000300596000044, The effects of an intense, high-frequency laser field linearly polarized along the growth direction on the binding energy of excitons confined in a GaInNAs/GaAs quantum well is computed for different nitrogen and indium mole fractions by means of a variational technique within the effective-mass approximation. Our results show that such laser field creates an additional geometric confinement on the electronic and exciton states in the quantum well and the exciton binding energy depends on both the nitrogen and indium concentrations. (C) 2011 Elsevier B.V. All rights reserved., Scientific and Technological Research Council of Turkey (TUBITAK) [COST 109T650], This work supported by The Scientific and Technological Research Council of Turkey (TUBITAK) for a research Grant COST 109T650.

WOS: 000298222800032, The effect of the intense laser field on the intersubband optical absorption for (1-2) transition in a Ga1-xInxNyAs1-y/GaAs single quantum well for different nitrogen and indium concentrations is investigated. The numerical calculations are performed in the effective-mass approximation. We have found that the increase of the nitrogen and indium concentrations with intense laser field leads to important effects on the optical properties of a quantum well. The obtained results show that the desired energy range corresponding to the subbands may be tuned by changing the laser intensity and the nitrogen and indium concentrations. This tunability gives a possibility for near-infrared electro-absorption modulators and quantum well infrared detectors. (C) 2011 Elsevier B.V. All rights reserved., TUBITAK (COST) [109T650]; COLCIENCIAS; CODI-Universidad de Antioquia (Estrategia de Sostenibilidad Grupo de Mate-ria Condensada-UdeA); Facultad de Ciencias Exactas y Naturales-Universidad de Antioquia (CAD); Excellence Center for Novel Materials/COLCIENCIAS [043-2005], This work supported by TUBITAK (COST) 109T650 and this research was partially supported by Colombian Agencies: COLCIENCIAS, CODI-Universidad de Antioquia (Estrategia de Sostenibilidad Grupo de Mate-ria Condensada-UdeA, 2010-2011), Facultad de Ciencias Exactas y Naturales-Universidad de Antioquia (CAD-exclusive dedication project 2010-2011), and the Excellence Center for Novel Materials/COLCIENCIAS (Contract no. 043-2005).

The effects of intense laser radiation on the exciton states in GaAs-Ga1‐xAlxAs quantum wells are studied with the inclusion of applied dc electric fields oriented along the growth direction of the system. The calculations are made within the effective mass and parabolic band approximations. The intense laser effects have been included along the lines of the Floquet method, modifying the confinement potential associated to the heterostructure. The results for the exciton binding energy, the energy of the exciton-related photoluminescence peak, and the carriers overlap integral are presented for several configurations of the quantum well size, the strength of the applied electric fields, and the incident laser radiation.

WOS: 000292828500003, By using the compact-density matrix approach, the effect of a nonresonant intense laser field on the linear and nonlinear optical absorptions based on intersubband transitions and the refractive index changes in an asymmetric semiconductor quantum well have been presented. Our results show that the peak position of the absorption coefficient is sensitive to intense laser field, the absorption maximum shifts towards lower energies for increasing intense laser field value. Also we observe as the intense laser field strength increases, the total refractive index change has been increased in magnitude and also shifted towards lower energies. The results indicate that linear and nonlinear optical properties of the low dimensional semiconductor heterostructures can be adjusted in a desired energy range by using intense laser field., TUBITAK (COST) [109T650]; COLCIENCIAS; CODI-Universidad de Antioquia; Facultad de Ciencias Exactas y Naturales-Universidad de Antioquia; Excellence Center for Novel Materials/COLCIENCIAS [043-2005], This work supported by TUBITAK (COST) 109T650 and this research was partially supported by Colombian Agencies: COLCIENCIAS, CODI-Universidad de Antioquia (Estrategia de Sostenibilidad Grupo de Mate-ria Condensada-UdeA, 2010-2011), Facultad de Ciencias Exactas y Naturales-Universidad de Antioquia (CAD-exclusive dedication project 2010-2011), and the Excellence Center for Novel Materials/COLCIENCIAS (Contract No. 043-2005).

WOS: 000292513700010, In this work are studied the intense laser effects on the impurity states in GaAs-Ga1- (x) Al (x) As quantum wells under applied electric and magnetic fields. The electric field is taken oriented along the growth direction of the quantum well whereas the magnetic field is considered to be in-plane. The calculations are made within the effective mass and parabolic band approximations. The intense laser effects have been included through the Floquet method by modifying the confinement potential associated to the heterostructure. The results are presented for several configurations of the dimensions of the quantum well, the position of the impurity atom, the applied electric and magnetic fields, and the incident intense laser radiation. The results suggest that for fixed geometry setups in the system, the binding energy is a decreasing function of the electric field intensity while a dual monotonic behavior is detected when it varies with the magnitude of an applied magnetic field, according to the intensity of the laser field radiation., COLCIENCIAS; CODI-Universidad de Antioquia (Estrategia de Sostenibilidad Grupo de Materia Condensada-UdeA); Facultad de Ciencias Exactas y Naturales-Universidad de Antioquia; El Patrimonio Autonomo Fondo Nacional de Financiamiento para la Ciencia, la Technologia y la Innovacion Francisco Jose de Caldas [275-2011]; Mexican CONACYT [CB-2008/101777]; CONACYT; The Scientific and Technological Research Council of Turkey (TUBITAK) [TUBITAK 109T650], This research was partially supported by Colombian Agencies: COLCIENCIAS, CODI-Universidad de Antioquia (Estrategia de Sostenibilidad Grupo de Materia Condensada-UdeA, 2009-2010, 2010-2011), Facultad de Ciencias Exactas y Naturales-Universidad de Antioquia (CAD-exclusive dedication project 2010-2011), and by "El Patrimonio Autonomo Fondo Nacional de Financiamiento para la Ciencia, la Technologia y la Innovacion Francisco Jose de Caldas" Contract RC - No. 275-2011. The work was developed with the help of CENAPAD-SP, Brazil. MEMR acknowledges support from Mexican CONACYT through research grant CB-2008/101777. CAD and MEMR are indebted to COLCIENCIAS and CONACYT for support under the bilateral project "Estudio de propiedades opticas y electronicas en nanoestructuras y sistemas semi-conductores de baja dimension". The authors are grateful to The Scientific and Technological Research Council of Turkey (TUBITAK) for a research grant (TUBITAK 109T650).

WOS: 000291420700007, 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(x)Ga(1-x)As quantum well for different well widths. The electronic structure of modulation-doped quantum well under the hydrostatic pressure is determined by solving the Schrodinger 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. (C) 2011 Elsevier Ltd. All rights reserved.

WOS: 000285408700084, In this work the effects of intense laser on the electron-related nonlinear optical absorption and nonlinear optical rectification in GaAs-Ga(1-x)Al(x)As quantum wells are studied under, applied electric and magnetic field. The electric field is applied along the growth direction of the quantum well whereas the magnetic field has been considered to be in-plane. The calculations were performed within the density matrix formalism with the use of the effective mass and parabolic band approximations. The intense laser effects are included through the Floquet method, by modifying the confining potential associated to the heterostructure. Results are presented for the nonlinear optical absorption, the nonlinear optical rectification and the resonant peak of these two optical processes. Several configurations of the dimensions of the quantum well, the applied electric and magnetic fields, and the incident intense laser radiation have been considered. The outcome of the calculation suggests that the nonlinear optical absorption and optical rectification are non-monotonic functions of the dimensions of the heterostructure and of the external perturbations considered in this work. (C) 2010 Elsevier B.V. All rights reserved., Colombian Agency: COLCIENCIAS; Colombian Agency: CODI-Universidad de Antioquia (Estrategia de Sostenibilidad Grupo de Materia Condensada-UdeA); Colombian Agency: Facultad de Ciencias Exactas y Naturales-Universidad de Antioquia; Colombian Agency: Excellence Center for Novel Materials/COLCIENCIAS [043-2005]; The Scientific and Technological Research Council of Turkey (TUBITAK) [TUBITAK 109T650], This research was partially supported by Colombian Agencies: COLCIENCIAS, CODI-Universidad de Antioquia (Estrategia de Sostenibilidad Grupo de Materia Condensada-UdeA, 2010-2011), Facultad de Ciencias Exactas y Naturales-Universidad de Antioquia (CAD-exclusive dedication project 2010-2011), and the Excellence Center for Novel Materials/COLCIENCIAS (Contract No. 043-2005). The authors are grateful to The Scientific and Technological Research Council of Turkey (TUBITAK) for a research grant (TUBITAK 109T650). CAD is grateful to Dr. Anna Kurczynska for useful discussions and the critical reading of the manuscript.

WOS: 000300022700001, Using the effective-mass approximation within a variational scheme, we have calculated the diamagnetic susceptibility and binding energy of a hydrogenic donor in a quantum well under different temperatures and hydrostatic pressure conditions. Our calculation have revealed the dependence of the diamagnetic susceptibility and the impurity binding on temperature and hydrostatic pressure.

The binding energy and diamagnetic susceptibility of a hydrogenic donor in a GaxIn1−xNyAs1−y/GaAs quantum well has investigated in the presence of the magnetic field by using a trial wave function in the framework of the effective mass approximation. The results show that the diamagnetic susceptibility and binding energy of the donor in the GaxIn1−xNyAs1−y/GaAs quantum well increases with nitrogen mole fraction. Also, we concluded that the incorporation of several percent of nitrogen in GaxIn1−xAs alloy causes a larger band gap difference between the well and barrier and therefore deeper quantum well, resulting in the stronger confinement of the donor electron and hence the smaller separation between the electron and impurity atom.

In this study, we have investigated theoretically the binding energies of shallow donor impurities in modulation-doped GaAs/Al 0.33 Ga 0.67 As double quantum wells (DQWs) under an electric field which is applied along the growth direction for different doping concentrations as a function of the impurity position. The electronic structure of modulation-doped DQWs under an electric field has been investigated by using a self-consistent calculation in the effective-mass approximation. The results obtained show that the carrier density and the depth of the quantum wells in semiconductors may be tuned by changing the doping concentration, the electric field and the structure parameters such as the well and barrier widths. This tunability gives a possibility of use in many electronic and optical devices.

WOS: 000271864200007, Valence band structure with spin-orbit (SO) coupling of GaAs/Ga1-xAlxAs square quantum well (SQW) under the electric field by a calculation procedure based on a finite element method (FEM) is investigated using the multiband effective mass theory ((k) over right arrow . (p) over right arrow method). The validity of the method is confirmed with the results of D. Ahn, S. L. Chuang and Y. C. Chang (J. Appl. Phys. 64 (1998) 4056), who calculated valence band structure, using axial approximation for Luttinger-Kohn Hamiltonian and finite difference method. Our results demonstrated that SO coupling and electric field have significant effects on the valence band structure., T. R. Prime Ministry State Planning Organization [DPT-120220], The authors would like to thank the T. R. Prime Ministry State Planning Organization for financial support (project No. DPT-120220).

WOS: 000259894100077, In this study, the intense laser-field dependence of intersubband absorption coefficient for 1-2 transition in GaAs/Ga1-xAlxAs DGQW under the electric field is investigated. The obtained results show that by changing the laser intensity together with the electric field and the well parameters (well and barrier widths) the desired energy range or spectral range of interest for intersubband and also interband absorption peak position may be tuned. This tunability gives a possibility for near-infrared electro-absorption modulators and quantum well infrared detectors. (C) 2008 Elsevier B.V. All rights reserved.

WOS: 000383985700007, The effects of nitrogen and indium concentrations on the 1s, 2s, 2p(0) and 2p +/--like donor impurity energy states in a single Ga1-xInxNyAs1-y/GaAs quantum well (QW) are investigated by variational approach within the effective mass approximation. The results are presented as a function of the well width and the donor impurity position. It is found that the impurity binding and transition energies depend strongly on the indium concentration while depends weakly on the nitrogen concentration.

WOS: 000235860200017, The binding energy of the donor in the triple-graded GaAs-(Ga,Al)As quantum well under the hydrostatic pressure, electric and magnetic fields are calculated by using a variational approach. The results have been obtained in the presence of hydrostatic pressure, magnetic and electric fields applied along the growth direction as a function of the impurity position without consideration of a mass mismatch or dielectric mismatch. (c) 2005 Elsevier B.V. All rights reserved.

WOS: 000232959400012, Using a variational approach, we have calculated the hydrostatic pressure and electric field effects on the donor-impurity related photoionization cross-section and impurity binding energy in GaAs/GaAlAs quantum well-wires. Both the results of impurity binding energy as a function of the impurity position and photoionization cross-section for a hydrogenic donor impurity placed at the center of the quantum well-wire as a function of the normalized photon energy in the quantum well-wire under the hydrostatic pressure and electric field which are applied to the z-direction for two different wire dimensions are presented. (c) 2005 Elsevier B.V. All rights reserved.

WOS: 000229921000007, The combined electric field and hydrostatic pressure effects on the binding energy of the donor impurity in double triangle quantum well (DTQW), double graded (DGQW) and double square (DSQW) GaAs-(Ga,Al)As quantum wells are calculated by using a variational technique within the effective-mass approximation. The results have been obtained in the presence of an electric field applied along the growth direction as a function of hydrostatic pressure, the impurity position, barrier width and the geometric shape of the double quantum wells. (c) 2005 Elsevier B.V. All rights reserved.

WOS: 000186497100020, By using an appropriate coordinate transformation, we have calculated variationally the ground state binding energy of a hydrogenic donor impurity in a quantum well in the presence of crossed electric and magnetic fields which are applied tilted at an angle to the layers. The dependence of the donor impurity binding energy on the well width, on the strength of the electric and magnetic fields, on the impurity position and on the directions of the external fields is discussed.

WOS: 000186949400032, The influence of a laser-field on the exciton binding energy and interband optical transitions in quantum-well wires is calculated by using a variational method and in the effective mass approximation. We conclude that in quantum-well wires the laser field amplitude provides an important, effect on the electronic and optical properties and the changes in the binding being dependent on the shape of the confinement potential. (C) 2003 Elsevier B.V. All rights reserved.

WOS: 000346845200030, This paper presents the results of the theoretical study of the effects of non resonant intense laser field and electric and magnetic fields on the optical properties (the linear and third order nonlinear refractive index and absorption coefficients) in an asymmetric quantum well. The electric field and intense laser field are applied along the growth direction of the asymmetric quantum well and the magnetic field is oriented perpendicularly. To calculate the energy and the wave functions of the electron in the asymmetric quantum well, the effective mass approximation and the method of envelope wave function are used. The asymmetric quantum well is constructed by using different aluminium concentrations in both right and left barriers. The confinement in the quantum well is changed drastically by either the effect of electric and magnetic fields or by the application of intense laser field. The optical properties are calculated using the compact density matrix approach. The results show that the effect of the intense laser field competes with the effects of the electric and magnetic fields. Consequently, peak position shifts to lower photon energies due to the effect of the intense laser field and it shifts to higher photon energies by the effects of electric and magnetic fields. In general, it is found that the concentration of aluminum, electric and magnetic fields and intense laser field are external agents that modify the optical responses in the asymmetric quantum well. (C) 2014 Elsevier B.V. All tights reserved., Scientific Research Project Fund of Cumhuriyet University [F-399, F-410]; CODI-Universidad de Antioquia; Facultad de Ciencias Exactas y Naturales-Universidad de Antioquia; EL PATRIMONIO AUTONOMO FONDO NACIONAL DE FINANCIAMIENTO PARA LA CIENCIA, LA TECNOLOGIA Y LA INNOVACION, FRANCISCO JOSE DE CALDAS; Mexican CONACYT [CB-2008-101777]; Escuela de lngenieria de Antioquia; EIA-UdeA, The authors are grateful to The Scientific Research Project Fund of Cumhuriyet University under the projects number F-399 and F-410. This research was partially supported by Colombian Agencies: CODI-Universidad de Antioquia (Estrategia de Sostenibilidad 2014-2015 de la Universidad de Antioquia), Facultad de Ciencias Exactas y Naturales-Universidad de Antioquia (CAD-exclusive dedication project 2014-2015), and by EL PATRIMONIO AUTONOMO FONDO NACIONAL DE FINANCIAMIENTO PARA LA CIENCIA, LA TECNOLOGIA Y LA INNOVACION, FRANCISCO JOSE DE CALDAS. MEMR acknowledges support from Mexican CONACYT through Grant CB-2008-101777, The Escuela de lngenieria de Antioquia co-supported EIA-UdeA project: Efectos de laser intenso sobre las propiedades opticas de nanoestrucuras semiconductoras de InGaAsN/GaAs y GaAlAs/GaAs. RLR is also grateful to the Physics Department of the Cumhuriyet University in Sivas-Turkey for the support and hospitality during his research stay.

WOS: 000366876100025, This paper presents the results of the theoretical study of the effects of non-resonant intense laser field and electric and magnetic fields on the optical properties in an quantum well (QW) make with Woods Saxon potential profile. The electric field and intense laser field are applied along the growth direction of the Woods Saxon quantum well and the magnetic field is oriented perpendicularly. To calculate the energy and the wave functions of the electron in the Woods Saxon quantum well, the effective mass approximation and the method of envelope wave function are used. The confinement in the Woods Saxon quantum well is changed drastically by the application of intense laser field or either the effect of electric and magnetic fields. The optical properties are calculated using the compact density matrix. (C) 2015 Elsevier Ltd. All rights reserved., Escuela de Ingenieria de Antioquia co; Colombian Agencies: CODI-Universidad de Antioquia (Estrategia de Sostenibilidad de la Universidad de Antioquia); Facultad de Ciencias Exactas y Naturales-Universidad de Antioquia (CAD-exclusive dedication project); PATRIMONIO AUTONOMO FONDO NACIONAL DE FINANCIAMIENTO PARA LA CIENCIA, LA TECNOLOGIA Y LA INNOVACION, FRANCISCO JOSE DE CALDAS, The Escuela de Ingenieria de Antioquia co-supported EIA-UdeA project: Efectos de laser intenso sobre las propiedades opticas de nanoestrucuras semiconductoras de InGaAsN/GaAs y GaAlAs/GaAs. This research was partially supported by Colombian Agencies: CODI-Universidad de Antioquia (Estrategia de Sostenibilidad 2014-2015 de la Universidad de Antioquia), Facultad de Ciencias Exactas y Naturales-Universidad de Antioquia (CAD-exclusive dedication project 2014-2015), and by EL PATRIMONIO AUTONOMO FONDO NACIONAL DE FINANCIAMIENTO PARA LA CIENCIA, LA TECNOLOGIA Y LA INNOVACION, FRANCISCO JOSE DE CALDAS.

WOS: 000360095000019, In this present work, the effects of the structure parameters such as the right-well width and the rightbarrier height on the linear, third-order nonlinear and total absorption and refractive index changes of asymmetric double semi-V-shaped quantum well are theoretically studied by using the compact-density matrix approach and iterative method. The electronic structure of this system is obtained by solving Schrodinger equation within the framework of effective mass approximation. Numerical results are presented for a typical GaAs/AlxGa1-xAs asymmetric double semi-V-shaped quantum well. The obtained results show that the right-well width and the right-barrier height have great effects on the optical characteristics of these structures. (C) 2015 Elsevier B.V. All rights reserved.

WOS: 000350075500023, 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 for transition between two lower-lying electronic levels in the step-like GaAs/Ga1-xAlxAs quantum well under external electric and magnetic fields are investigated. The calculations were performed within the compact density-matrix formalism with the use of the effective mass and parabolic band approximations. The obtained results show that both total absorption coefficient and refractive index change are sensitive to the well dimensions and the effects of external fields. By changing the intensities of the electric, magnetic and non-resonant intense laser fields together with the well dimensions, we can obtain the blue or red shift, without the need for the growth of many different samples. (C) 2015 Elsevier B.V. All rights reserved., Cumhuriyet University [F-410]; Colombian Agencies: CODI-Universidad de Antioquia. (Estrategia de Sostenibilidad de la Universidad de Antioquia); Facultad de Ciencias Exactas y Naturales-Universidad de Antioquia(CAD-exclusive dedication project); EL PATRIMONIO AUTONOMO FONDO NACIONAL DE FINANCIAMIENTO PARA LA CIENCIA; LA TECNOLOGIA Y LA INNOVACION, FRANCISCO JOSE DE CALDAS; Mexican CONACYT [CB-2008-101777]; EIA-UdeA project: Efectos de laser intenso sobre las propiedades opticas de nanoestrucuras semiconductoras de InGaAsN/GaAs y GaAlAs/GaAs; Physics Depai linent of the Cumhuriyet University in Sivas, Turkey, The authors are grateful to The Scientific Research Project Fund of Cumhuriyet University under the project number F-410. This research was partially supported by Colombian Agencies: CODI-Universidad de Antioquia. (Estrategia de Sostenibilidad 2014-2015 de la Universidad de Antioquia), Facultad de Ciencias Exactas y Naturales-Universidad de Antioquia(CAD-exclusive dedication project 2014-2015), and by EL PATRIMONIO AUTONOMO FONDO NACIONAL DE FINANCIAMIENTO PARA LA CIENCIA, LA TECNOLOGIA Y LA INNOVACION, FRANCISCO JOSE DE CALDAS. MEMR acknowledges support from Mexican CONACYT through Grant CB-2008-101777. The Escuela de Ingenieria de Antioquia co-supported EIA-UdeA project: Efectos de laser intenso sobre las propiedades opticas de nanoestrucuras semiconductoras de InGaAsN/GaAs y GaAlAs/GaAs. RLR is also grateful to the Physics Depai linent of the Cumhuriyet University in Sivas, Turkey for the support and hospitality during his research stay.

WOS: 000085453200026, The binding energy of excitons in symmetric and asymmetric coupled double GaAs/Ga1-xAlxAs quantum wells is calculated by using a variational approach. The results have been obtained in the presence of a uniform magnetic field, as a function of the potential symmetry, size of the quantum well and coupling parameter of the wells. We show that by increasing the applied magnetic field one can obtain large binding between electrons and holes which is similar to the change in the dimensions of the structure. This behaviour in the excitonic binding for different wells and barrier geometries can be used to study these systems in regions of interest, without the need for the growth of many different samples.