Theoretical and Experimental Demonstration of Orbital Angular Momentum (OAM) States Measurements of Vortex Beams with Annular Gratings

We present a simple and efficient scheme to measure OAM states (i.e. topological charge values) of vortex beams with annular gratings. By observing the diffraction patterns, we can detect high-order vortex beams with topological charge value as high as ±10.