  We introduce a quantum like representation of a Spiral Phase Plate, acting on
an electromagnetic field, as a two mode phase operator. The representation is
based on the Newton binomial expansion and on properties of rational power of
lowering and raising operators of quantum field. The correctness of this
representation is proved by obtaining the same results of the Paul's operator
in the single mode limit and comparing the results of two particular problems
solved both in the classical and quantum picture: the action of a Spiral Phase
Plate on a Gaussian Beam (corresponding to the vacuum state of the
two-dimensional harmonic oscillator) and on a off-axis Gaussian Beam
(corresponding to the displaced vacuum state in quantum picture).
