High conversion efficiency of second-harmonic generation in step quantum wells

Abstract
Second‐harmonic generation due to intersubband transitions in GaAs/AlxGa1−xAs step quantum well structures has been studied with a tunable TEA CO2 laser. The maximum value of χ(2)(2ω) is found to be ∼9×10−7 m/V. Using a multipass or ‘‘waveguide’’ structure, a conversion efficiency of more than 3×10−4 has been obtained.