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

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 Ga(0.6)Al(0.4)As barrier, a 4.5-nm Ga(0.4)Al(0.09)As step barrier, and a 6-nm GaAs well, is pumped by a CO(2) TEA laser. The saturation of second-harmonic conversion is found to occur near 16 MW/cm(2). The power conversion efficiency is measured to be of the order of 3.4 x 10(-4). These results are in good agreement with theoretical predictions from a density matrix treatment.