  Recent studies show that the angular momentum, both spin and orbital, of
rotating light beams possesses counter-intuitive characteristics. We present a
new approach to the question of orbital angular momentum of light based on the
complex massless scalar field representation of light. The covariant equation
for the scalar field is treated in rotating system using the general
relativistic framework. First we show the equivalence of the U(1) gauge current
for the scalar field with the Poynting vector continuity equation for paraxial
light, and then apply the formalism to the calculation of the orbital angular
momentum of rotating light beams. If the difference between the co-, contra-,
and physical quantities is properly accounted for there does not result any
paradox in the orbital angular momentum of rotating light. An artificial
analogue of the paradoxical situation could be constructed but it is wrong
within the present formalism. It is shown that the orbital angular momentum of
rotating beam comprising of modes with opposite azimuthal indices corresponds
to that of rigid rotation. A short review on the electromagnetism in
noninertial systems is presented to motivate a fully covariant Maxwell field
approach in rotating system to address the rotating light phenomenon.

General Physics;Optics