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. 
D. Neshev (1), A. Dreischuh (1), G.G. Paulus (2), H. Walther (2,3)   ((1) Sofia University, Dept. of Quantum Electronics, So...