Detailed analysis of the intersubband absorption in a GaAs stepped quantum well for quadratic detection and second harmonic generation

Abstract

We focus on intersubband transitions tunability in GaAs stepped quantum wells through the step's width variation. A double resonance can then occur due to two-photon absorption with possible promising nonlinear optics applications in absorption or emission. In this work, we identified five structures where the equidistant two-photon absorption (ETPA) is possible. We have evaluated the potential of each structure for quadratic detection (QD) and/or second harmonic generation (SHG). This was accomplished quantitatively through the analysis of the calculations results of the main terms of the nonlinear factors involved in both processes. These calculations are based on those of the optical physical parameters linked to the intersubband absorption, namely the individual absorption coefficients and the corresponding dipolar momentum couplings. To highlight the enhancing effect of the asymmetry degree on the total absorption, an investigation of the optical absorption properties of symmetrical quantum wells was done in parallel.