Evaluation of second-order susceptibility in a symmetrical GaAs/InGaAs/GaAs quantum well under-indium segregation effect

The second-order susceptibility in a symmetrical two-level GaAs/InGaAs/GaAs quantum well under the indium segregation effect introduced by Muraki's model is theoretically analyzed in this study. The simulation procedure involves solving the coupled Schrödinger-Poisson equations to determine the electronic band structure, using the envelope wave function and the effective mass approximations. Then, the second harmonic generation (SHG) coefficient is calculated in a two-level model from the density matrix formalism. The study examines the influence of indium composition, hydrostatic pressure, external electric field and delta doping on electronic band parameters as well as on the second order susceptibility. The results obtained reveal that:(i) The resonant peaks' intensities of the second harmonic generation (SHG) increase along with indium composition as well as hydrostatic pressure, while their energy positions shift to higher and lower energies, respectively, with the increase of indium composition and that of the hydrostatic pressure. (ii) The simultaneous employment of an applied electric field and the delta doping in InGaAs' well is used to adjust the overlap of the electronic wave functions and the subbands' densities. This allows for a significant increase in real and virtual resonant intensities of the peaks reaching a value up to 5x10⁻⁵ mV⁻¹ and shifting them towards higher energies. The results of this work open new perspectives for the exploitation of nonlinear and optical properties related to intersubband transitions in the structure of the quantum well based on GaAs/InGaAs highlighting their considerable potential for the development of advanced optoelectronic devices.