All-optical phase-independent logic elements based on phase shift induced by coherent soliton collisions

We demonstrate, for the first time to our knowledge, that a fast coherent collision between two Kerr spatial solitons can give rise to a significant phase shift for both interacting beams. The maximal collision-induced phase shift /spl ap//spl pi/ rad takes place when the amplitudes of the solitons are equal (/spl eta//sub 1/=/spl eta//sub 2/) and the length of the interaction zone is comparable with a soliton phase period. Depending on the ratio /spl eta//sub 2///spl eta//sub 1/, and the collision angle between the solitons, the magnitude of the phase shift can be varied within a reasonable range, for example from 180/spl deg/ to 40/spl deg/. The analysis of the effect performed by the finite-difference beam-propagation method has shown that it is insensitive to the initial phase difference between the incident beams (/spl delta//sub i/), even in the case when /spl eta//sub 1//spl ne//spl eta//sub 2/. It has been demonstrated that the phenomenon can be used for all-optical three-soliton logic elements, which are capable of providing more than 3-dB signal amplification and possess bi -independent output characteristics.