Near-infrared non-degenerate two-photon absorption coefficients of bulk GaAs and Si.

We investigate the non-degenerate two-photon absorption coefficient β(ω, ω) as a function of the non-degeneracy parameter ω/ω for bulk GaAs and Si at a constant transition energy + =1.57eV. In both materials, the two-photon absorption strength increases with increasing ω/ω regardless of the direct and indirect character of the bandgap. The GaAs measurement data agrees well with corresponding theoretical predictions for direct semiconductors. The Si data reveals similar trends albeit with smaller overall absorption strength. In addition, different crystallographic orientations and polarization configurations are analyzed.