Dynamics of nonlinear waves in optical waveguides

It is shown that spatial solitary-wave emission is not just a one-dimensional phenomenon but survives in two transverse dimensions under two fundamentally different waveguide geometries. One geometry is a symmetric slab waveguide with linear substrate, linear film, and nonlinear cladding, analogous to the 1-D case. A cylindrically symmetric Gaussian input field is injected into the slab. At low powers it diffracts within the slab, but at higher powers a solitary wave is emitted into the cladding. As the power is increased further, multi-solitary-wave emission is observed, pairs of which combine to form oscillatory bound states. The other geometry is a cylindrically symmetric linear fiber core bound by a nonlinear cladding. The fiber is monomode, and at low powers the injected Gaussian beam closely matches the guided mode. At higher powers, one or more concentric rings is emitted. For a saturation index change on the order of twice the linear index step, the emitted rings have peak intensities that fairly well saturate the index change, and the rings are stable. When the saturation index is five or more times as large as the linear index step, the emitted rings break their azimuthal symmetry, and a collection of 4n solitary waves is formed, of which n = 1, 2, 3 and 4 have been observed. These solitary waves interact with each other, forming complex turbulent patterns while exchanging energy.