Directional coupling of optical signals by odd dark beams with mixed phasedislocations

Numerical simulations on the evolution of step-screw and edge-screw optical phase dislocations in bulk saturable self-defocusing nonlinear media an pr esented, with emphasis on their ability to induce steering waveguides for s ignal beams (pulses). Two schemes for directional coupling of such signals, both ensuring a reasonable coupling-to-crosstalk efficiency ratio, are inv estigated. The parameters useful for performance optimization of the couple rs are discussed.