Three-frequency interactions of high-intensity light waves in media with quadratic and cubic nonlinearities

It is shown that in phase-matched parametric processes and second harmonic generation in noncentrosymmetric media in high-intensity optical fields, an important part may be played by the cubic nonlinearity of the medium that results in disruption of the optimal phase relationship between the interacting waves. As a result, the maximum efficiency of nonlinear conversion of the optical frequencies of the plane waves differ from 100% and the spatial beat frequency also varies. Frequency doubling is particularly sensitive to the influence of the cubic nonlinearity. Numerical calculations of the efficiency of nonlinear processes are given for KPD and LiNbO₃ crystals.