  We analyze wave propagation in coupled planar waveguides, pointing specific
attention to modal cross-talk and out-of-plane scattering in quasi-planar
photonics. An algorithm capable of accurate numerical computation of wave
coupling in arrays of planar structures is developed and illustrated on several
examples of plasmonic and volumetric waveguides. An analytical approach to
reduce or completely eliminate scattering and modal cross-talk in planar
waveguides with anisotropic materials is also presented.
