Analyzing global parameters of tunable vector vortices generated via conjugate mode interference

Abstract

We have demonstrated a method to generate and continuously tune the spatial polarization of optical vector vortex beams. The coherent combination of two optical vortex beams with opposite topological charge and orthogonal circular polarization is achieved using a conjugate mode interferometer to generate optical vector vortex beams. A step neutral density filter is used in one of the arms of the interferometer for controlling the phase and intensity of one of the interfering beams which thereby affects the spatial polarization distribution of the resultant beam. Beams with symmetrical and asymmetrical spatial polarization distribution are generated experimentally by tilting the neutral density filter. Additionally, a set of global parameters that characterize the vector nature of vector vortex beams are discussed and found that the experimental results are in good agreement with the simulated results. The experimentally generated beams are found to have more than 90 % mode purity. This method is a useful tool for small angle sensing, fast switching and continuous tuning of the spatial polarization of vector vortices.