Interband second-harmonic generation in ${\mathrm{Zn}}_{1\mathrm{-}\mathit{x}}$${\mathrm{Cd}}_{\mathit{x}}$Se/ZnSe strained quantum wells

We report continuous-wave interband second-harmonic generation (SHG) at 460–480 nm in strained ${\mathrm{Zn}}_{1\mathrm{-}\mathit{x}}$${\mathrm{Cd}}_{\mathit{x}}$Se/ZnSe asymmetric quantum wells grown by molecular-beam epitaxy. The dependence of the SHG intensity on the fundamental frequency allowed us to identify the individual quantum-well exciton resonances in the second-harmonic signal. The strongest SHG was found to be associated with light-hole exciton transitions. Numerical calculations of the SHG intensity that take into account exciton and continuum states yielded predictions in remarkable agreement with experiment.