Abstract
The possibility of the surface‐emitting second‐harmonic generation (SHG) based on intersubband transitions in multiple quantum‐well (QW) structures is examined theoretically. The critical role of valence band mixing is demonstrated. The off‐diagonal SHG coefficients, necessary for the surface‐emitting SHG, are evaluated for the transitions between the valence subbands in GaAs/AlAs QW structures are found to be comparable in magnitude to the diagonal SHG coefficients reported in literature.