We investigate numerically interactions between two bright or dark incoherentlocalized beams in an strontium barium niobate photorefractive crystal in onedimension, using the coherent density method. For the case of bright beams, ifthe interacting beams are in-phase, they attract each other during propagationand form bound breathers; if out-of-phase, the beams repel each other and flyaway. The bright incoherent beams do not radiate much and form long-livedwell-defined breathers or quasi-stable solitons. If the phase difference is$\pi/2$, the interacting beams may both attract or repel each other, dependingon the interval between the two beams, the beam widths, and the degree ofcoherence. For the case of dark incoherent beams, in addition to the above theinteractions also depend on the symmetry of the incident beams. As alreadyknown, an even-symmetric incident beam tends to split into a doublet, whereasan odd-symmetric incident beam tends to split into a triplet. When launched inpairs, the dark beams display dynamics consistent with such a picture and ingeneral obey soliton-like conservation laws, so that the collisions are mostlyelastic, leading to little energy and momentum exchange. But they also radiateand breathe while propagating. In all the cases, the smaller the intervalbetween the two interacting beams, the stronger the mutual interaction. On theother hand, the larger the degree of incoherence, the weaker the interaction.
展开▼
