THEORY OF ANISOTROPY OF TWO-PHOTON ABSORPTION IN ZINC-BLENDE SEMICONDUCTORS

The influence of the higher ${\mathrm{\ensuremath{\Gamma}}}_{15}^{\mathit{c}}$ conduction-band set on the strength of the two-photon-absorption coefficient, the two-photon linear/circular dichroism, and the two-photon-absorption anisotropy is calculated across the spectral region below the fundamental absorption edge, for the cubic materials GaAs and InSb. The anisotropy is entirely due to the higher band and is predicted to produce up to a 70% variation in the two-photon-absorption coefficient of GaAs as the relative orientation of the optical polarization to the crystal axes is altered. This is in good agreement with recent experiments.