Directions In Optical Angular Momentum
  For paraxial and non-paraxial light, numerous measures of electromagnetic attribute are expressible in terms of photon annihilation and creation. Accordingly, energy, angular momentum and chirality measures acquire a consistent interpretation. From the photonic nature of light, it emerges that an infinite hierarchy of spin-type measures depend on a difference in number operators for modes of opposing helicity, pure circular polarization giving maximal values. Measures of orbital angular momentum are determined by a sum of corresponding number operators. By analysis of electric and magnetic features in the reflection of circular polarizations, regions of prominent chiral interaction in the interference are identified. 
Matt M. Coles and David L. Andrews
physics.optics quant-ph