One of the solutions of the
Helmholtz equation is the vortex beams. In the
recent decades, production and applications of
these types of beams have found serious
attentions. Determination of the vortex beam
topological charge and its sign are very
important issues. Odd number of reflections of the vortex beam changes its vorticity. In this paper, we have used a q-plate to generate a vortex beam from a plane wave of a He-Ne laser beam and a two-channel moiré based wavefront sensor is used to measure wavefront gradient of the vortex beam. In two different arrangements the vortex beam experience odd and even number of reflections, respectively, and from the moiré pattern deformations the topological charge of the vortex beam and its sign are determined.
کلید واژگان :
moiré deflectometry, vortex beam, topological charge, reflection effect on the topological charge
