Ultrafast laser propagation in waveguide arrays

Nonlinear refractive index generated by ultrashort pulse laser in waveguide array leads normally to discrete nonlinear localization and discrete spatial soliton. By the simulation, it is shown that the nonlinear localization depends on the refractive index changes of waveguide array. While refractive index changes of waveguide array is small, the delocalization is possible. Nonlinear localization and delocalization are decided by the relationship between initiate refractive index change of waveguide array, nonlinear refractive index, and saturation refractive index change which corresponds to optimal coupling constant. The nonlinear localization and delocalization are also observed by using a high repetition- rate femtosecond laser inscription waveguide array injected by low repetition rate femtosecond laser.