Nondegenerate three-photon absorption in zinc-blende semiconductors

A prescription for determining the nondegenerate three-photon absorption spectrum of zinc-blende semiconductors is presented. Theoretical calculations based on third-order perturbation theory and Kane's band structure provide the nondegenerate three-photon absorption coefficient for any combination of photon energies and polarizations. The enhancement over three orders of magnitude is predicted when using extremely nondegenerate photon energies, which is greater than that predicted with two-photon absorption. A large polarization dependence is predicted for excite-probe measurements (two photons absorbed from the excitation and one from the probe), with variation between parallel and perpendicular polarizations of up to a factor of 10 with a significant spectral dependence. Experimental measurements on zinc-blende GaAs and ZnSe show excellent agreement with the predicted spectral shape, nondegenerate enhancement, and polarization dependence. In addition, wurtzite CdS also shows a large enhancement over the degenerate case.