Nonlinear guided waves in a negative-index slab waveguide

We report the existence of nonlinear waves propagating in a waveguide composed of a negative-index medium surrounded by conventional media, i.e. in a slab waveguide with a negative-index nonlinear core. We study the dispersion relation of found modes and calculate the associated energy flow. Finally, we discuss other possible mode families of the structure. Their shape depends on the sign of the magnetic permeability of the cladding layers.