Control of the second- and third-order nonlinearities in GaAs-AlGaAs multiple quantum wells

We report the use of impurity-free vacancy disordering techniques to control the nonlinear optical properties of GaAs-AlGaAs multiple quantum wells. These processes result in a shift in the position of the absorption edge to higher energy and have been used to modify the second-and third-order nonlinear coefficients. Working at photon energies just below the half bandgap we have observed a reduction of similar to 50% in the value of nonlinear refractive coefficient n(2) for a bandgap shift of around 40 nm. This change arises due to the combined effects of increasing the bandgap and increasing the detuning. The process can also result in a modulation in the magnitude of the second-order susceptibility chi((2)) coefficient and provides a potential mechanism for realizing quasi-phase-matched structures.