Interaction of photovotaic spatial solitons between dark and dark as well as dark and bright

The parallel interaction between two photovoltaic spatial solitons of dark and dark as well as dark and bright with different wavelengths is investigated by numerical method. Our numerical study indicates that the dark solitons can both remain as quasi soliton form in certain distance while they propagate coaxially. However, they attract each other while closely overlapping. And they have a convergent effect on each other at the slowly varying region of optical field while in larger separations. For the case of interaction between dark and bright, the bright one may experience compression, expansion or energy transfer depending on their mutual separation. The physical interpretation of this solitons interaction is also given in terms of the refractive index waveguide they jointly induce.