OACs with the variation of incident photon wavelength λ as a function of L_w2 for Zn_{1 − xl}Mg_xlO/ZnO/Zn_{1 − xc}Mg_xcO/ZnO/Zn_{1 − xr}Mg_xrO ADQWs with L_b1 = 4 nm, L_w1 = 5 nm, L_b2 = 7 nm, xl = 0.6, xc = 0.4, and xr = 0.4, for the transition from (a) E₁ to E₂, (b) E₂ to E₃, and (c) E₁ to E₃. The right images are for ADQW1, the left ones are for ADQW2.