Transformation of multi-edge-dislocations to screw-dislocations in optical field

Transformation of edge-dislocations to screw-dislocations in the optical field is experimentally and numerically demonstrated. A special multi-edge-dislocation structure is designed by arranging multiple edge-dislocations, which have the same phase-step value, periodically along the azimuthal orientation. Experimentally, in virtue of the computer-generated holography, a Gaussian beam is modulated by the multi-edge-dislocation, whose propagation dynamics is investigated as well. The results reveal that the multi-edge-dislocation can be converted into a screw-dislocation with the evolution of the Gaussian beam into a vortex-like beam. What is more, the sum phase change of the dislocations is conserved in this process. Then, the experimental results are verified by numerical simulations, and discussed in detail by analyzing the evolutions of the linear momentum density. Furthermore, the influence of the phase-step value of the edge-dislocation on the transformation is discussed, which illustrates the quantitative relation between the phase-step value and the topological charge of crew-dislocation.