Beam propagation study of nonlinear coupling between transverse electric modes of a slab waveguide

The evolution of an optical field along a symmetrical slab waveguide capable of supporting two TE modes in the linear regime is investigated using the beam propagation method (BPM) where the waveguide and cladding media have a uniform, self-focusing Kerr law nonlinearity. BPM calculations agree well with coupled-mode theory at low input powers, but diverge at powers approaching the coupled-mode value of the critical power and above, due to self-focusing of the field. At high power, the beam splits into two parts which generate unusual long-range collision effects.