Discrete solitons in arrays of positive and negative index waveguides.

We report on existence and properties of discrete solitons in arrays of alternating waveguides with positive and negative refractive indices. When the nonlinearities of all waveguides are focusing, we found solitons only in the semi-infinite gaps. Finite gap solitons found for waveguides having nonlinearities of different types reveal the symmetry breaking in the Fourier space. It is found that there exist more than one soliton families bifurcating from the gap edges of the linear spectrum. The field distribution in such multichannel couplers reveals nonexponential decay and nonmonotonic dependence of the energy growth in the positive index waveguides on the strength of losses in the negative index waveguides.