Spiral wave formation in nonlinear diffraction interaction

The formation of a spiral wave is addressed through theoretical study of a three level laser and with the investigation of the diffraction role in the spiral forming process in optics as compared with that of diffusion in hydrodynamics. The numerical simulations established that creation of a wavefront with open ends is necessary as prerequisite for forming of spiral waves in diffraction interaction. Diffraction in this system adjusts the normal wavefront velocity away from the free ends and near the tips to induce a normal velocity profile which imposes on the free edges of the wavefront. The nonlinear interaction between spiral waves lead to shock waves which bound them in turn screen their interaction, resulting in stable, spatial structures.