Photonic measures of helicity: optical vortices and circularly polarized reflection.

For both paraxial and nonparaxial light, numerous electromagnetic quantities are expressible in terms of photon annihilation and creation operators. Accordingly, measures of energy, angular momentum, and chirality 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, with pure circular polarization giving maximal values. Measures of orbital angular momentum are determined by a sum of corresponding number operators. Analysis of the electric and magnetic fields in the reflection of circular polarizations reveals regions of prominent chiral interference.