Symmetry-induced anisotropy of two-photon absorption spectra in zinc-blende semiconductors

The anisotropy of degenerate two-photon absorption spectra is calculated for various zinc-blende compound semiconductors by using ab initio full band structures in the local-density approximation and the microscopic response theory. Anisotropy in the E-1 absorption region is noted in the present paper, the origin of which is discussed based on the ab initio calculational results. The anisotropy magnitude in the E-1 absorption region has a nearly constant value (similar to 0.5) hardly depending on material kinds, which is quite different from the case in the E-0 absorption region where the anisotropy shows the strong material dependence. By a qualitative analysis using the k . p perturbation method, this behavior ol anisotropy is explained to occur due to the wave-function symmetry, i.e., due to where in the Brillouin zone the two-photon transitions occur.