Tuning optical absorption and refractive index in coupled GaAs quantum dots via impurity position and electric field

In this work, we theoretically investigate the effects of the electric field (EF), structural parameters, and impurity position on the linear and third-order nonlinear optical absorption coefficients, as well as on the refractive index change, in a parallelepiped GaAs four-quantum-dot system embedded in an Al x Ga 1 − x As matrix. The impurity and the external EF are aligned along the x-direction, enabling direct interaction with the confined electronic states. The calculations are performed within the effective mass approximation using the finite element method. The results show that the optical response is highly sensitive to the impurity location, which significantly affects both the amplitude and spectral position of the absorption and refractive index peaks. In addition, quantum size effects, relaxation rate, and incident field intensity strongly influence the optical behaviour through their impact on confinement and transition characteristics.