Abstract

In the last few years, photorefractive (PR) screening solitons have attracted considerable research interest. They emerge when laser beams of appropriate wavelength, intensity, and shape are launched into a PR crystal, and a dc electric field is applied across it, in order to induce self­focusing of beams through PR screening. According to their unique properties, PR solitons seem very promising for all-optical applications, such as soliton-induced guiding or switching. Some preliminary experimental results on two interacting solitons in two transverse dimensions have been presented recently [1]. Coherent solitons display both attraction and repulsion, depending on the phase difference between them. Since they tend to build diffraction gratings and exchange energy, incoherent beams are more manageable, but it was believed [2] that they can only attract. We demonstrate numerically that two-dimensional incoherent solitons display both attraction and repulsion and we observe interesting propagation effects. If two solitons are launched parallel in the plane perpendicular to the direction of the applied field, they only attract and fuse, staying in the plane. If the launching plane is parallel to the applied field, then the solitons either repel or attract, depending on their distance. And if the plane is at an angle to the applied field, then the solitons oscillate or rotate (Fig. 1), strongly depending on their initial position and distance.

© 1998 IEEE