Investigation of fractional charge OAM beam generation and its decomposition

We demonstrate fractional orbital angular momentum (OAM) beams generated using a spiral phase plate (SPP) from a Gaussian input beam. The phase properties of these beams are studied experimentally using Mach-Zender interferometer technique. The generated fractional OAM beams are explained by decomposing them into sum of Laguerre Gaussian (LG) modes. The analysis presented is useful in determining the prominent charge value, different higher order mode content in OAM beam and also helps to estimate its purity. This modal analysis is expected to be useful in OAM beams based communication system for spatial mode filtering at the receiving end of the link and also to obtain purity of OAM beams.