Propagation dynamics of optical vortices in Laguerre-Gaussian beams

We have calculated the propagation dynamics of an initial off-axis vortex with topological charge I in Laguerre-Gaussian background beams (LGO and LGO), which are examples of background beams with non-generic dislocation surfaces, on which the real and imaginary parts of the light field are zero. When initially a vortex with broad core (e.g., r-vortex) is embedded in the background beam, the dislocation surfaces are destroyed during propagation and two vortices with opposite charge are created per dislocation surface in planes perpendicular to the propagation direction. For a vortex with narrow core (e.g., point vortex) diffraction is important and leads to the birth of more than two vortices per dislocation surface. These results are also valid for other background beams with dislocation surfaces, e.g., Hermite-Gaussian and Ince-Gaussian beams. We investigated experimentally the spatial evolution of the intensity distribution of an initial off-axis vortex with narrow core and topological charge 1 in LGO and LGO background beams. The experimental results are in good agreement with the calculated intensity distributions. (c) 2005 Elsevier B.V. All rights reserved.