Mid-infrared second-order nonlinear susceptibility in InAs/GaAs quantum dots

Intersublevel second-order nonlinear susceptibility is investigated in InAs /GaAs self-assembled quantum dots. It is shown that the nonlinear susceptib ility associated with intersublevel transitions in the conduction band or i n the valence band can be greatly enhanced by up to six orders of magnitude as compared to the susceptibility of bulk GaAs. This enhancement results f rom the nanometer scale of the intersublevel dipoles and from the achieveme nt of resonance conditions between the pump and harmonic waves and the invo lved intersublevel transitions. Experimentally, second-harmonic generation is observed in the valence band of the dots. A double resonance condition f ulfilled at 168 meV leads to an enhancement of three orders of magnitude of X-zxx((2)) as compared to the susceptibility of bulk GaAs.