Influence of electric and magnetic fields on the nonlinear optical rectification of a shallow donor in four-quantum dot structures

The current study investigates the contribution of external electric and magnetic fields on the nonlinear optical rectification (NOR) in a system composed of four $GaAs$ quantum dots situated in an ${{Al}_{\alpha }Ga}_{1-\alpha }As$ matrix, taking into account the presence of a shallow donor impurity bound to an electron. The subband energy levels, geometric factors, and corresponding wave functions are determined through the solution of the Schrödinger equation using the finite element method. Our main results show that x-polarised incident light induces stronger second-order nonlinear optical impacts in the studied four-quantum-dot system compared to y and z polarization. Also, the outcomes suggest that the electric field (E-field) significantly alters the NOR response by breaking spatial symmetry and shifting both the amplitude and energy of the peaks. Magnetic fields further enhance the NOR response, particularly at positions of strong electron localization. These findings demonstrate the high tunability of nonlinear optical properties in coupled quantum dot systems and support their application in advanced optoelectronic devices.