Characterizing the fractional coherence vortices through the area of the intensity cross-correlation function.

We have generated the fractional coherence vortices using the speckle patterns obtained from the scattering of the fractional vortex beams. In this study, we found the topological charge of the fractional vortex beam with a resolution of 0.01 using the area of the coherence function of scattered fractional optical vortex beams. We have also provided accuracy for the measurement of topological charges of fractional vortex beams using the studies of the area of the coherence function. Our experimental results are well matched with the theoretical results. These fractional coherence functions can be used to generate a security key for data authentication and data encryption. In addition, fractional vortex beams have multiple OAM modes and can be used to address the explosive growth in free-space optical communication.