Topological activity in Bragg elliptical twisted fibers.

We have theoretically shown that Bragg twisted elliptical fibers manifest, in certain spectral regions, the property of topological activity--the ability to change in the reflected field the topological charge of incoming optical vortices and fundamental modes by two units. This property could be used for narrowband generation of optical vortices from Gaussian beams and for changing the topological charge of incoming optical vortices.

Generation and conversion of optical vortices in long-period twisted elliptical fibers.

We theoretically demonstrate that long-period twisted elliptical fibers have the ability to change in a certain wavelength range the topological charge of the incoming field by two units. We also show that such fibers can generate charge-2 optical vortices from the incoming Gaussian beams.