abstract
- We propose an off-axis superposition of vector modes with orthogonal polarizations, constructed from a general scalar helical vortex mode with unknown topological charge m, as a method to measure its orbital angular momentum. We derived analytic expressions for sets of solutions to find lines of linear polarization (L lines) within the composite polarization field. We found that the solutions corresponding to the angular component of the composite field depend only on the displacement of the beams and the topological charge m, and they are invariant under propagation and changes in the relative amplitude and phase between the beams. © 2014 IOP Publishing Ltd.