Generation and conditional switching of isolated C-points in optical beam output of few-mode fiber

Abstract

We demonstrate here an experimental observation on generation and conditional switching between π-symmetric isolated C-points such as lemon and star in a few mode optical fiber. This scheme is of potential advantage in switching between lemon and star by controlling either polarization or phase helicities of the vortex modes involved in the formation of singular pattern. A half wave plate and a cylindrical lens are used at the fiber output end for this purpose. These singular patterns can be generated from the fiber through the combination of orthogonally polarized Gaussian and vortex modes co-excited simultaneously by controlling the coupling conditions at the launching end.