Measuring Singularities of Vector Structured LG Beams and Stokes Vortices via Intensity Moments Technique

Abstract

We theoretically and experimentally investigated the transformation processes of polarization singularities (C-points, L-lines, V-points and rings, as well as the Stokes vortices) in vector structured Laguerre–Gaussian (sLG) beams with varying their controllable phase parameters. It was shown that all the Stokes vortices simultaneously turn to zero only in V-points and rings, in other polarization singularities only a part of the Stokes vortices vanish. On the basis of our computer simulation, the process of the birth and annihilation of polarization singularities has been studied. In the experiment, we used the intensity moments technique for the first time to measure the spectrum of vector modes and their digital multiplexing of a simple vector sLG₁₂ beam. The amplitude and phase spectra were measured in each linear polarized component of the space-variant polarization field. Then scalar fields of the polarization components were formed, which was the digital demultiplexing of the vector sLG field. The combination of the vector modes made it possible to restore the vector sLG beam again, that is the digital multiplexing the vector field.