First-principles calculation of nonlinear optical susceptibilities in GaAs

The frequency-dependent second- and third-order nonlinear optical susceptibilities in GaAs are calculated using a first-principles approach based on the band structure obtained by the self-consistent orthogonalized linear combinations of atomic orbitals method. The results compare well with experimental data. It is shown that inclusion of accurate high-lying conduction-band states is absolutely essential for a well-converged result. Miller's rule is found to be obeyed in GaAs only for frequencies up to 2 eV.