Cascaded second-order nonlinearity in nonuniformly temperature tuned LiNbO3 channel waveguide

We have demonstrated by changing the temperature scan speed the possibility of achieving different temperature profiles, therefore different wave-vector mismatch along the LiNbO₃ optical channel waveguide. We can control the sign of the induced large nonlinear phase shift in the small fundamental depletion region, which is very useful in applications. We also tried to adjust the scan speed to obtain the uniform temperature profile. Theoretical explanations of the experimental results have been given