Anisotropy of two-photon absorption in GaAs and CdTe

The anisotropy in the two-photon absorption coefficient for GaAs and CdTe is reported for the first time. Variations of the order of 15% are observed at room temperature in the magnitude of the nonlinear absorption, and are seen to increase at 85^∘{}K, as the angle of the polarization vector of the incident 1.06-{μ}m light is changed with respect to the crystal axes. The variation agrees with the predictions of nonlinear optics and a simple three-band model (neglecting excitons), but is too large at 85^∘{}K to be accounted for by the band model.