  Bessel beams are studied within the general framework of quantum optics. The
two modes of the electromagnetic field are quantized and the basic dynamical
operators are identified. The algebra of these operators is analyzed in detail;
it is shown that the operators that are usually associated to linear momentum,
orbital angular momentum and spin do not satisfy the algebra of the translation
and rotation group. In particular, what seems to be the spin is more similar to
the helicity. Some physical consequences of these results are examined.
