Midinfrared second-harmonic generation in p-type InAs/GaAs self-assembled quantum dots

Abstract
Resonant second-harmonic generation is reported in InAs/GaAs self-assembled quantum dots. Frequency doubling is observed between confined states in the valence band of the quantum dots. The second-order nonlinear susceptibility is maximum at 168 meV (7.4 μm wavelength) and is observed for an in-plane polarized excitation. A value of χzxx(2) as large as 2×10−7 (m/V) is measured for one dot plane. A three-dimensional numerical calculation of the valence band states shows that the second-harmonic generation involves a resonant excitation between the h000 and h101 states and a state close to the continuum wetting layer states.