THE NONLINEAR-OPTICAL PROPERTIES OF ALGAAS AT THE HALF BAND-GAP

We report experimental values for the nonlinear optical coefficients o f AlGaAs, in the half-band-gap spectral region. The dispersion of the nonlinear refractive-index coefficient, nl, is measured for both TE- a nd TM-polarized light. We observe n(2)(TE) > n(2)(TM) and a ratio of c ross-phase modulation to self-phase modulation (TE) of similar to 0.95 , as predicted from bandstructure calculations. The spectral dependenc e of the two- and three-photon absorption coefficients are also measur ed, Finally, the implications for all-optical switching and spatial so liton propagation are discussed.