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    Electric field effect on the intersubband optical absorption of GeSn quantum wells with parabolically graded barriers
    (Academic Press Ltd- Elsevier Science Ltd, 2023) Yahyaoui, N.; Baser, P.; Said, M.; Saadaoui, S.
    In this study, we propose a theoretical simulation of a Ge0.9Sn0.1 rectangular SQW with GeSn parabolically graded barriers (PGBs) in the terahertz (THz) region. The discrete intra-band confined energy levels and their matching wave functions were calculated by solving the stationary Schr & ouml;dinger equation by the finite difference method taking into account the Compact Density Matrix approach under the framework of both the effective mass and the envelope wave function approximations. In this work, we studied the effect of the quantum square-well width on the intersubband transition and oscillator strength in a GeSn-strained-based Barrier-Well-Barrier GeSn/(Ge,alpha-Sn) PGBs to obtain the optimum quantum confinement of electrons. The electronic states and their wave functions in the conduction band were computed by solving the Schr & ouml;dinger equation without and under the effect of an applied external electric field at room temperature. We then investigated the effect of the electric field on the optical absorption coefficient (OAC). Our numerical results show that for external fields (>15 kV/cm), an intersubband transitions (ISBTs) frequency band of 2-14 THz (8-58 meV) was obtained for the specific optimized parameters. These results should be beneficial to the design of devices based on GeSn QWs with PGB structures operating in the THz frequency range.
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    Machine learning algorithms for predicting the photoionization cross section of CdS/ZnSe core/shell spherical quantum dots surrounded by dielectric matrices
    (Elsevier B.V., 2025) Cherni, A.; Zeiri, N.; Yahyaoui, N.; Baser, P.; Said, M.; Saadaoui, S.; Murshed, Mohammad N.
    In this study, we explore the prediction of the photoionization cross section (PCS) of CdS/ZnSe core/shell spherical quantum dots (CSQD) surrounded by different dielectric matrices. The quantum dot systems, embedded in polyvinyl alcohol (PVA), polyvinyl chloride (PVC), and silicon dioxide (SiO2) matrices, were modeled under varying core-shell dimensions and dielectric environments. Our findings show that the resonant peak of the PCS experience a redshift with improvement in their amplitude in the case of the PVA matrix, while in the case of the PVC and SiO2 the magnitude of the PCS is reduced and their resonant peak suffers a blueshift. Three different machine learning algorithms were used to estimate the photoionization cross-section, namely Artificial Neural Networks (ANN), Decision Trees (DT), and Random Forest Regressors (RFR). Among these, Random Forest Regression proved to be the most successful algorithm, particularly for the SiO2 matrix, achieving exceptional performance with the coefficient of determination R2 = 0.999 Mean Squared Error MSE=10-4 and the Root Mean Squared Error RMSE=0.0077. While DT exhibited lower MSE, MAE, and RMSE than ANN in the SiO2 matrix, ANN showed potential in capturing more complex nonlinear relationships. These results demonstrate the superior predictive capabilities of RFR and highlight the applicability of machine learning in modeling quantum dot systems. This work offers valuable insights into the optimization of optoelectronic device design through accurate and efficient computational methods. © 2025 The Author(s)
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    Theoretical modeling of nonlinear optical properties in spheroidal CdTe/ ZnTe core/shell quantum dot embedded in various dielectric matrices
    (Elsevier, 2024) Hertilli, S.; Yahyaoui, N.; Zeiri, N.; Başer, Pınar; Said, M.; Saadaoui, S.
    The theoretical investigation of the electronic and nonlinear optical properties in spheroid-shaped CdTe/ZnTe core/shell quantum dots (CSQDs) embedded into two commonly adopted dielectric matrices (PVA, SiO2) is done in the framework of the Effective Mass Approximation (EMA). The discrete intra-band confined energy levels and their matching wave functions were calculated by solving the stationary Schro center dot dinger equation taking into ac-count the Compact Density Matrix (CDM) approach. The effect of the dielectric mismatch between the system and the capped matrix has been studied and discussed. Our numerical results revealed that the third-order nonlinear (TON) optical susceptibility chi(3) is strongly influenced by the geometrical parameters and the dielectric environment.