Multiphoton light absorption in crystals with structure of diamond and zinc blende

A theoretical study is made of the two- and three-photon absorption of light in germanium and III-V semiconductors. It is shown that, if the anisotropy of the valence-band electrons and the contribution of virtual states from distant bands to the many-photon absorption are taken into account, the polarization dependence of the many-photon absorption coefficient is anisotropic for the aforementioned crystals. The initial optical spin polarization of free carriers is calculated for the two-photon excitation with circularly polarized light and an arbitrary ratio of the gap to the spin-orbit splitting of the valence band. (author)