D. E. Edmundson and R. H. Enns, "Fully 3-dimensional collisions of bistable light bullets," Optics Letters. 18, 1609 (1993).

To break cylindrical symmetry and achieve fully 3-dimensional collisions of bistable light bullets, the effect of a varying impact parameter has been numerically investigated. Novel effects such as soliton tunnelling and spiral arm formation have been observed, some of which have no direct 1-dimensional analog. The extreme stability and attractor-like behavior of optical bullets is demonstrated.