We report the first observation of self-trapping of a spatially incoherent optical beam in a nonlinear medium. Self-trapping occurs in both transverse dimensions, when diffraction is exactly balanced by photorefractive self-focusing. [S0031-9007(96)00610-2]

No abstract

We report the observation of three-dimensional spiraling collision of interacting two-dimensional spatial solitons. The solitons are photorefractive screening solitons and are phase incoherent to each other at all times. The collision provides the solitons with angular momentum which is manifested in a centrifugal repulsion force. When it is balanced by attraction, the solitons spiral about each other in a DNA-like structure. [S0031-9007(97)

No abstract

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

We study one-dimensional steady-state photorefractive screening solitons in a bulk strontium barium niobate crystal. We compare measurements and calculations of the soliton properties and find good agreement for relations between the profile, width and intensity of the soliton, the applied voltage and material parameters. We find the solitons stable against perturbations both in the plane and perpendicular to the plane of the soliton for intensities large compared to the background intensity.

We study experimentally steady-state photorefractive screening solitons trapped in both transverse dimensionsand measure their beam profiles as they propagate throughout the crystal. The solitons are observed to be axially symmetric, and they self-bend. We characterize the soliton dependence on the optical intensity, appliedelectric-field strength, and beam diameter.

We report the observation of incoherent collisions between two-dimensional bright photorefractive screening solitons. The solitons remain intact and do not exchange energy whenever the collision angle exceeds thecritical angle for guidance in the waveguide that each soliton induces, which is, in turn, fully controlled by the soliton parameters. When the collision angle is much smaller than the critical angle the solitons fuse to form a single beam.