Third-order anisotropies in cubic crystals

Abstract
Third-order difference-frequency generation of the type ω = 2ω1 − ω3 has been used to determine accurately the cubic nonlinearities of various crystals of the space group Fm3m. The samples were rotated under well-defined polarization conditions of the incoming fields of frequencies ω1 and ω3. Ratios of anisotropic to isotropic contributions have been derived, and an attempt has been made to obtain absolute nonlinear susceptibility data by comparison with BK7 glass.