Interactions between counter-propagating photovoltaic spatial solitons

We study the interactions between two counter-propagating photovoltaic spatial solitons with different frequencies. Numerical results show that these two solitons display different dynamic characteristics during spatial evolution, which also differ obviously from the case of co-propagation. These two solitons exhibit different induced focusing or defocusing behavior when they propagate coaxially, which is sensitive to the specimen length. When they propagate in parallel and closely overlapping, the induced focusing or defocusing effects are weakened and the soliton with higher frequency attracts the one with lower frequency markedly. And their evolutions are different from the case of co-propagation.