Nonlinear phase shift without cascaded second-order processes and third-order nonlinearity

A new mechanism for obtaining a nonlinear phase shift has been proposed and schemes are described for its implementation. As it is shown, the interfer ence of two waves with intensity-dependent amplitude ratio coming from the second-harmonic generation should produce the nonlinear phase shift. The si gn and amount of nonlinear distortion of a beam wavefront is dependent on t he relative phase of the waves that is introduced by the phase element. The calculated value of n(2)(eff) exceeds that connected with cascaded quadrat ic nonlinearity, at the same conditions.