Spiraling behavior of photorefractive screening solitons

The question of spiraling or no spiraling of incoherent screening spatial s olitons in photorefractive crystals is addressed by a careful numerical ana lysis. We find that the interaction of solitons typically results in an ini tial mutual rotation of their trajectories, followed by damped oscillations and the fusion of solitons. The rotation can be propelled to prolonged spi raling by the skewed launching of beams. This behavior is caused by the ani sotropy of the refractive index change in the crystal. [S0031-9007(98)08275 -1].