  We report on existence and properties of discrete gap solitons in zigzag
arrays of alternating waveguides with positive and negative refractive indices.
Zigzag quasi-one-dimensional configuration of waveguide array introduces strong
next-to-nearest neighbor interaction in addition to nearest-neighbor coupling.
Effective diffraction can be controlled both in size and in sign by the value
of the next-to-nearest neighbor coupling coefficient and even can be cancelled.
In the regime where instabilities occur, we found different families of
discrete solitons bifurcating from gap edges of the linear spectrum. We show
that both staggered and unstaggered discrete solitons can become highly
localized states near the zero diffraction points even for low powers.
Stability analysis has shown that found soliton solutions are stable over a
wide range of parameters and can exist in focusing, defocusing and even in
alternating focusing-defocusing array.
