Second-order nonlinear optical susceptibilities in asymmetric coupled quantumwells

Abstract

The second harmonic generation (SHG) in the asymmetric coupled quantum wells(ACQWs) is studied theoretically for different widths of the right-well and the barrier. Theanalytical expression of the SHG susceptibility is deduced by using the compact densitymatrix approach and the iterative method. Numerical calculations are presented for typicalGaAs/AlxGa1−xAs ACQWs.The results show that the calculated SHG susceptibility in this coupled system can reach a magnitudeof 10−5 m V−1, 1–2 orders higher than that in single quantum systems. Moreover, the SHGsusceptibilities are not monotonic functions of the widths of the right-well and thebarrier, but have complex relationships with them. The calculated results alsoreveal that by adjusting the widths of the right-well and the barrier respectively, aset of optimal structural parameters can be found for obtaining a strong SHGsusceptibility.