Exploring the Nonlinear Optical Behaviour of InGaAs/GaAs Triple Quantum Wells via Structural Modulations and External Electric Fields

The nonlinear optical properties of the InxGa1-xAs/GaAs triple quantum well structure are studied for different structure parameters and applied external electric field. Within the framework of the effective mass and envelope function approximations, the one-dimensional time-independent Schrödinger wave equation is solved using the diagonalization method to obtain the energy eigenvalues and eigenfunctions of the structure. The coefficients of nonlinear optical properties such as nonlinear optical rectification (NOR), second harmonic generation (SHG), and third harmonic generation (THG) of the structure are numerically evaluated from the corresponding expressions derived within the compact density matrix approximation. The influence of adjustable structure parameters and the applied external electric field affects the separation of subband energy levels and the magnitudes of dipole moment matrix elements. These changes in the electronic properties of the structure cause the NOR, SHG, and THG peak positions to shift towards lower or higher energy regions. It is expected that these results will enable the appropriate design of new optoelectronic devices.