Direct measurement of cascaded nonlinearity in lithium niobate channel waveguides

We report on interferometric measurements of nonlinear phase shifts of the fundamental mode that are due to cascading in a second-harmonic-generation experiment in lithium niobate channel waveguides. With temperature tuning of the wave-vector mismatch the nonlinear phase shifts were adjustable in sign and magnitude. Varying the wave-vector matching condition along the waveguide leads to large phase shifts with low depletion and dispersion of the fundamental.