Abstract
The optimal design for infrared second harmonic generation (SHG) is determined for a GaAs-based quantum device using a recently developed genetic approach. Both the compositional parameters and electric field are simultaneously optimized, and the quantum limit for SHG, set by the trade-off between large dipole moments (favoring electron delocalization) and large overlaps (favoring electron localization), is determined. Optimal devices are generally obtained that have an asymmetric double quantum well shape with narrow barriers and a graded region sideways to the largest well. An electric field is not found to lead to improved SHG if the compositional parameters are optimized.