Nonlinear Interband Optical Response in Excitonic δ ‐Doped GaAs/AlGaAs Multiple Quantum Wells Under External Fields, Pressure, Temperature and Barrier Width Effects

This work presents a detailed theoretical study of the linear and third‐order nonlinear optical properties of excitonic δ ‐doped GaAs/AlGaAs multiple quantum wells under an external magnetic field. The electronic structure is modelled within the effective mass approximation, and the correlated excitonic states are obtained by diagonalising the full electron–hole Hamiltonian in a realistic multi‐well potential using a centred finite‐difference method. The Coulomb interaction is treated using a softened potential appropriate for quasi‐one‐dimensional confinement. The model incorporates band offsets, pressure‐ and temperature‐dependent material parameters and magnetic field–induced confinement effects. The linear and third‐order nonlinear optical absorption coefficients, along with the associated refractive index changes, are calculated using the density‐matrix formalism. Magnetic fields (1–5 T) induce blue shifts of 6–12 meV with reduced peak intensity. Increasing barrier width (2–6 nm) produces larger blue shifts (30–40 meV), while pressure and temperature cause characteristic blue and red shifts, respectively. These results demonstrate tuneable excitonic energies and nonlinear optical responses in engineered multiple quantum wells for tuneable photonic device applications. A rigorous theoretical analysis of excitonic linear and third‐order nonlinear optical responses in δ ‐doped GaAs/AlGaAs multiple quantum wells is presented. The electron–hole interaction is treated using a regularised Coulomb potential. The combined influence of magnetic field, hydrostatic pressure, temperature and barrier widths reveals rich and controllable optical behaviour, offering insights for advanced optoelectronic device design.