Multiphoton absorption and nonlinear refraction of GaAs in the mid-infrared

We report the wavelength dependencies of the two- and three-photon absorption coefficients of undoped GaAs in the spectral range 1.3-3.5 mu m, as well as nonlinear refractive index n(2) in the range 1.7-3.25 mu m. The data were obtained by using the single-beam Z-scan method with 100-fs-long optical pulses. Anisotropy of the three-photon absorption coefficient was observed and found to be consistent with the crystal symmetry of GaAs. (c) 2007 Optical Society of America.