Quasi-phase-matched second-harmonic generation in reflection from AlxGa1-xAs heterostructures

Quasi-phase-matched second-harmonic (SH) generation in reflection geometry is described and demonstrated. The SH intensity can be strongly enhanced by spatially modulating the optical properties of the nonlinear medium. This type of quasi-phase-matching is demonstrated by using an Al0.8Ga0.2As/GaAs heterostructure designed for λ = 1.06 μm incident light. The SH light intensity generated in reflection from the heterostructure is enhanced 70 times relative to the SH response of a homogeneous GaAs wafer. A resonant cavity design that employs this structure to make thin films with extremely high SH generation efficiencies is proposed.