Formation and light guiding properties of dark solitons in one-dimensional waveguide arrays

We report on the formation of dark discrete solitons in a nonlinear periodic system consisting of evanescently coupled channel waveguides in defocusing lithium niobate. Localized nonlinear dark modes displaying a phase jump in the center that is located either on-channel (mode A ) or in-between channels (mode B ) are formed, which is to our knowledge the first experimental observation of mode B . By numerical simulations we find that the saturable nature of the nonlinearity is responsible for the improved stability of mode B . The ability of the induced refractive index structures to guide light of a low-power probe beam is demonstrated.