Measurement of Orbital Angular Momentum of Light using Stokes Parameters and Barnett's Formalism

We present a formalism for experimental determination of the orbital angular momentum (OAM) of a paraxial optical beam-field by intertwining Barnett's formalism and Stokes parameter measurements. Using Barnett's formalism we calculate the OAM flux density of a suitably general 2-dimensional beam-field; and re-express it in terms of experimentally measurable quantities. Considering a demonstrative optical system, we obtain the OAM flux density profiles, total OAM flux and OAM per photon -- leading towards the experimental characterization of OAM using Barnett's formalism. Our method will find potential applications in nano-optical processes involving the transfer of electromagnetic OAM to particles and across interfaces.