Tunable Second-Harmonic Generation in “4-3” tuned Quantum Wells Driven by Electric Fields

In this study, we investigate the influence of external electric fields on the potential profile, energy states, dipole moment matrix elements (DMMEs), and second-harmonic generation (SHG) in the “4-3" GaAs/AlGaAs quantum wells (QWs). By varying the electric field strength, pronounced modifications are observed in electron localization within the coupled wells, accompanied by notable shifts in the energy levels. A transition from an asymmetric to a symmetric potential profile occurs at a critical field of F = 57 kV/cm, leading to an equal distribution of electrons across both wells. The SHG response exhibits a strong dependence on the applied field: a redshift dominates below the critical field, while a blueshift emerges above it, and the SHG coefficient vanishes completely at the symmetric configuration. These results demonstrate that external electric fields provide an effective mechanism for tuning the nonlinear optical properties of the 4-3 QWs, offering potential applications in nano optoelectronic and photonic devices.