Directional coupling of optical signals by odd dark beams with mixed phase dislocations

Numerical simulations on the evolution of step-screw and edge-screw optical phase dislocations in bulk saturable self-defocusing nonlinear media are presented, with emphasis on their ability to induce steering waveguides for signal beams (pulses). Two schemes for directional coupling of such signals, both ensuring reasonable coupling-to-cross-talk efficiency ratio, are investigated. The parameters useful for performance optimization of the couplers are discussed.