Collisions of light bullets of different circular polarization

For a locally isotropic focusing Kerr medium with anomalous chromatic dispersion, collisions of left- and right-polarized spatiotemporal optical solitons have been numerically simulated. Stable propagation of such ``light bullets'' in a moderate nonlinear regime is supported by a transverse parabolic profile of the refraction index in a multimode waveguide. In such systems, the transverse motion of centers of mass of wavepackets occurs on classical trajectories of the harmonic oscillator, while the longitudinal motion is uniform. Therefore tangent collisions of two solitons are possible as well as head-on collisions. As the result, an inelastic collision between two solitons with opposite circular polarizations can produce either two binary light bullets containing the left and the right polarization in some proportion, or more evolved bound structures.