The non parabolicity and the enhancement of the intersubband absorption in GaAs/GaAlAs quantum wells

We have performed calculations of the transition energies in a GaAs/AlGaAs quantum well with 38% of Aluminum. Three energy levels could be confined below a certain well width leading to two allowed transitions. Calculations were made in both the parabolic and the non parabolic cases. While the E23 transition stands above the E12 one in the first case, there is a clear crossing between these two transitions in the second case for a specific geometry (Lw = 7.7 nm). This suggests the possible enhancement in the absorption if a radiation has the appropriate frequency such that hν=E12=E23. This interesting proposition was investigated after the comparison of the absorption coefficient calculations for two different geometries. Such structures may be used in two photons absorption devices because the E3 level is close to the continuum.