Abstract

The interaction of photorefractive (PR) solitons has attracted considerable research interest in recent years. Screening solitons emerge when laser beams of appropriate wavelength, intensity, and shape are launched into a PR crystal and a de electric field is applied across, to induce self-focusing of beams through PR screening. The material response is an inherently anisotropic and nonlocal function of the propagating light intensity. The interaction between solitons is anomalous, in that they experience both attraction and repulsion. This feature prevents stable spiraling, and the beams oscillate about each other and eventually fuse [1]. There is a different approach [2], which asserts that the PR screening process can be represented by isotropic models. Here the refractive index is locally modified and under proper initial conditions two solitons start to spiral about each other. We integrate both models for exactly the same initial and boundary conditions, and display how the differences evolve. Although allowed, isotropic modeling of the solitons imposes constraints on the general description in two transverse dimensions, which are not warranted from the physical point of view. Even such a simplified picture of material response does not allow for prolonged spiraling, owing to the nonconservation of angular momentum. We find that isotropic models should be used for short propagation distances and for qualitative purposes only.

© 2000 IEEE