title: Rotation of Electromagnetic Fields and the Nature of Optical Angular Momentum.
abstract: The association of spin and orbital angular momenta of light with its polarization and helical phase fronts is now well established. The problems in linking this with electromagnetic theory, as expressed in Maxwell's equations, are rather less well known. We present a simple analysis of the problems involved in defining spin and orbital angular momenta for electromagnetic fields and discuss some of the remaining challenges. Crucial to our investigation is the duplex symmetry between the electric and magnetic fields.
authors.affiliation: Department of Physics, SUPA, University of Strathclyde, Glasgow G4 0NG, UK ; Department of Physics, FNSPE, Czech Technical University in Prague, Břehová 7, 115 19 Praha 1, Czech Republic.
authors.forename: Stephen M
authors.initials: SM
authors.lastname: Barnett
keywords: optical angular momentum