Optical vortices in helical fiber gratings

One of the topical problems in fiber singular optics is concerned with the study of generation conversion and controlling optical vortices in optical fibers. In this work we address the question of evolution of optical vortices in multihelicoidal fibers – the optical fibers with a chiral symmetry. We show that such systems are able to carry out operations with the topological charge of the incoming optical field. Also we demonstrate that at certain conditions such fibers can generate optical vortices from regular incoming beams. Introducing defects into the structure of multihelical fibers allows one to control the intensity orbital angular momentum and topological charge of the vortex fields.