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The authors study experimentally the coherent collision of two one-dimensional spatial bright solitons in a photorefractive crystal. Depending on the relative phase of the solitons and their intersecting angle, effects such as fusion, energy exchange and soliton birth have been observed. The experimental and numerical results are in good agreement.
Introduction: Spatial optical solitons have been suggested for all-optical guiding and switching in nonlinear-optical media. The predictions and observations of optical spatial solitons in nonlinear materials, which require considerably less laser power than Kerr-type materials, are the subject of increasing interest. Spatial solitons in photorefractive crystals (PRCs), for example, have been observed [1 - 4]. These soliton-induced waveguides can be used to guide and steer another optical beam, which in this case constitutes the simplest optical element. One of their more promising characteristics for practical applications in photonics are the structures formed by intersecting waveguides such as X or Y junctions [5, 6]. Such intersecting waveguides can be implemented by colliding two or more solitons. Recently collision between mutually incoherent 2D spatial solitons in an SBN crystal was reported in [7], interaction forces between one-dimensional spatial solitons in parallel propagation were observed in [8], and the fusion and birth of 2D spatial solitons caused by the collision and annihilation of photorefractive solitons was reported in [9, 10].
Experimental resnlts: The experimental setup used to study the soliton collision was similar to that used in our previous investigations of soliton interactions [8]. One He-Ne CW laser beam 1 (X = 632.8nm) was expanded and collimated and split into two beams of equal intensity by means of a cube beam splitter and subsequently recombined. The two beams were focussed by means of a cylindrical lens. Separation of the beams was controlled using one of the minors of a Michelson interferometer. The relative phase between the beams was controlled by means of a mirror mounted upon a piezoelectric transducer, allowing for variable delay (and relative phase) between the two beams when a DC field drove the transducer. We obtained appropriate widths (13 jim FWHM) for the beams arriving at the SBN crystal (6 x 6 x 6 mm3) by using the cylindrical lens. The trajectories...