  We theoretically and experimentally investigate type II second harmonic
generation in III-V-on-insulator wire waveguides. We show that the propagation
direction plays a crucial role and that longitudinal field components can be
leveraged for robust and efficient conversion. We predict that the maximum
theoretical conversion is larger than that of type I second harmonic generation
for similar waveguide dimensions and reach an experimental conversion
efficiency of 12 %/W, limited by the propagation loss.
