Analysis of fractional vortex beams using a vortex grating spectrum analyzer

Abstract

We demonstrate that an optical vortex with fractional topological charge can be approximated as a linear combination of the two adjacent integer topological charges. This theory is experimentally verified utilizing a vortex grating spectrum analyzer, i.e., a computer-generated hologram with a charge 1 vortex grating. By extracting the intensity value of the center portion of the target diffraction orders, both the number and the sign of the topological charge of any input vortex can be identified and analyzed.