Saturation of second-harmonic generation in GaAs–AlGaAs asymmetric quantum wells

Abstract
The saturation of second-harmonic generation is observed for the first time to our knowledge in GaAs–GaAlAs asymmetric quantum wells. The sample, which consists of 200 periods of a 30-nm Ga0.6Al0.4As barrier, a 4.5-nm Ga0.91Al0.09As step barrier, and a 6-nm GaAs well, is pumped by a CO2 TEA laser. The saturation of second harmonic conversion is found to occur near 16 MW/cm2. The power conversion efficiency is measured to be of the order of 3.4 × 10−4. These results are in good agreement with theoretical predictions from a density matrix treatment.