We present an experimental and numerical investigation of the interaction of bidirectional self-guided beams in photorefractive media. Distinct from copropagating beams, the feedback intrinsic to the counterpropagating geometry renders such configurations unstable beyond a control parameter threshold. The instability is mediated through attractive interaction between the induced waveguides and leads to dynamic states, showing telltale signs of chaotic behaviour. We demonstrate qualitative correspondance between experiment and a saturable Kerr model, investigate the dynamical bifurcation in detail and expand on the consequences of a realistic photorefractive model including nonlocality, anisotropy and self bending.
Dynamical behavior of counterpropagating (CP) incoherent laser beams in photorefractive crystals is investigated. We perform experimental study displaying rich dynamics of three-dimensional CP optical solitons and formulate theory capable of capturing such dynamics. We find that our numerical simulations qualitatively agree with experimental findings for various CP beam structures. We also study numerically CP vortices in photorefractive crystals, in both space and time. The propagation of more complex CP beam arrangements, such as arrays of vortices, is also considered, and the transition from a few-beam propagation behavior to the transverse pattern formation dynamics is followed.