Propagation and stability of two-colour spatial optical solitons

Two-colour spatial solitons comprise coupled nonlinear optical beams at two distinct temporal frequencies [1]. The components (which may be bright-like and/or dark-like) are localized in space and tend to overlap, thereby allowing \nthe interplay between diffraction and nonlinear effects to result in stationary light structures. We will propose a more complete and realistic model for describing such phenomena. A key feature of our approach is that one may access multicolour geometries involving beam propagation at arbitrary angles and orientations with respect to the reference direction – such considerations are central to multiplexing and interface scenarios, but lie far outside the reach of conventional theory. The modulational instability problem can be solved in a range of physically relevant regimes, and extensive computations have \nconfirmed theoretical predictions. New families of exact analytical two-colour solitons are reported, each of which has co-propagation and counter-propagation classes that are related by geometrical transformation.