Spatio-temporal dynamics of counterpropagating photorefractive self-trapped beams

We investigate spatio-temporal dynamics in the interaction of counterpropagating self-trapped beams in a photorefractive strontium barium niobate crystal. While the interaction of copropagating spatial optical solitons exhibits only transient dynamics, resulting in a final steady state, the counterpropagating geometry supports a dynamic instability mediated by intrinsic feedback. Experimental observations are compared to and found to be in qualitative agreement with numerical simulations. The threshold of the instability is examined numerically and period doubling beyond the bifurcation is demonstrated.