The nonlinear optical properties of AlGaAs at the half band gap

We report experimental values for the nonlinear optical coefficients of AlGaAs, in the half-band-gap spectral region. The dispersion of the nonlinear refractive-index coefficient, nl, is measured for both TE- and TM-polarized light. We observe n(2)(TE) \u3e n(2)(TM) and a ratio of cross-phase modulation to self-phase modulation (TE) of similar to 0.95, as predicted from bandstructure calculations. The spectral dependence of the two- and three-photon absorption coefficients are also measured, Finally, the implications for all-optical switching and spatial soliton propagation are discussed