  This paper analyzes the algebraic and physical properties of the spin and
orbital angular momenta of light in the quantum mechanical framework. The
consequences of the fact that these are not angular momenta in the quantum
mechanical sense are worked out in mathematical detail. It turns out that the
spin part of the angular momentum has continuous eigenvalues. Particular
attention is given to the paraxial limit, and to the definition of
Laguerre--Gaussian modes for photons as well as classical light fields taking
full account of the polarization degree of freedom.
