Tunable Second-Harmonic Generation in Asymmetric Triple-Gaussian Quantum Wells Reshaped by an Intense Laser Field

In this study, the second-harmonic generation (SHG) coefficient of a GaAs/AlGaAs asymmetric triple Gaussian quantum well (ATGQW) structure is investigated under the influence of an intense laser field (ILF). The results reveal that the applied ILF significantly reshapes the QW profile, leading to a laser-dressed potential with a modified confinement profile. As the laser-dressing parameter α_0 increases, the individual wells begin to merge, causing electrons to localize within a reduced number of QWs. Consequently, the system exhibits a decreasing effective number of QWs: while the structure contains three wells at α_0 = 0, it transitions to two wells at α_0 = 10 nm and a single well at α_0 = 20 nm. This behavior directly affects the energy level differences, the dipole moment matrix elements (DMMEs), and therefore the SHG coefficients. The transition energies E_21 and E_31/2 show a nonlinear dependence on the ILF strength, whereas the product of the DMMEs reaches a pronounced maximum at α_0 ≈ 9 nm and rapidly decreases for higher ILF values due to the enhanced localization of electrons in narrower regions. These findings demonstrate that the ILF serves as an efficient control mechanism capable of dynamically tuning the effective well count and strongly modulating the nonlinear optical response of semiconductor QW systems.