We demonstrate experimentally collisions between vector ( Manakov-like) solitons that involve energy exchange at large collision angles, for which scalar solitons pass through one another practically unaffected. PACS numbers: 42.65.Tg, 05.45.Yv Vector solitons consist of two (or more) components that mutually self-trap in a nonlinear medium. They were first suggested by Manakov [1] for the Kerr nonlinearity, which is proportional to the intensity. The Manakov system leads to two coupled cubic nonlinear Schrödinger equations and is integrable and soluble analytically. Temporal Manakov-like solitons were proposed [2] and demonstrated in single mode optical fibers [3], and spatial ones were demonstrated in planar waveguides [4]. Vector solitons were also suggested [5] and observed [6] in a dark-bright form: when one of the components is a bright soliton and the other dark. Following the discovery of photorefractive spatial solitons, vector (Manakov-like) solitons were also suggested in photorefractives. In contrast to the Kerr nonlinearity, the photorefractive nonlinearity is saturable, but coincides with the Kerr nonlinearity in the limit of very low intensities [7]. One form of vector solitons found in photorefractives is of particular interest, because it applies to any noninstantaneous nonlinearity and allows more than two components: vector solitons based on mutual incoherence between the vector constituents [8]. Observations of such two-component vector solitons followed soon thereafter in three realizations: bright-bright, dark-dark, and dark-bright coupled pairs [9]. Finally, vector solitons can be realized as multimode [2,10] and multihump solitons which were recently demonstrated experimentally using the mutual-incoherence method [11].Interactions between solitons are fascinating, since in many aspects solitons interact like particles: they pass through one another [12], undergo elastic collisions [13], and, in saturable nonlinearities [14], undergo fusion [15], fission and annihilation [16], and can even spiral about each other [17]. Soliton interactions depend on the number of soliton components. Thus far, interactions between vector solitons were studied theoretically only [1,18,19], with the exception of one experiment demonstrating a bound state between two dark-bright solitons [20].Here, we demonstrate experimentally interactions between vector solitons, highlighting features that are nonexistent for scalar solitons in the same regime: energy exchange at large collision angles, that is, in the regime where scalar solitons simply pass through each other [12].Consider the coupled nonlinear wave equations for the slowly varying amplitudes of two EM fields, A͑x, z͒ and B͑x, z͒, in a ͑1 1 1͒D system in which x and z are the transverse and longitudinal coordinates, respectively, µ ≠ ≠z 2 i 2k ≠ 2 ≠x 2
