Ultrafast two-photon nonlinearities in CdSe near 1.5 /spl mu/m studied by interferometric autocorrelation

We have used interferometric autocorrelation measurements to study the femtosecond nonlinear optical properties of bulk CdSe crystals in the wavelength region just above the half gap wavelength of 1.42 /spl mu/m. Between 1.42 and 1.55 /spl mu/m, we measured an ultrafast third-order nonlinearity with nonlinear refractive index n/sub 2/=1.3/spl times/10/sup -13/ cm/sup 2//W/sup -1/. Detailed modeling of the autocorrelations revealed the influence of higher order effects due to free carriers generated by nonlinear absorption. We find that CdSe is an interesting alternative material to AlGaAs for applications in this technologically important wavelength region.