It is shown here that st straightforward procedure can be used to quantize
the linearized equations for an electromagnetic field in a plasma. This lea
ds to a definition of an effective mass for the transverse photons, and a d
ifferent one far the longitudinal photons, or plasmons. Both masses are sim
ply proportional to the electron plasma density. A nonlinear perturbative a
nalysis can also be used to extend the quantization procedure, in order to
include the ponderomotive force effects. This leads to the definition of a
photon charge operator. The mean value of this operator, for a quantum stat
e with a photon occupation number equal to 1, is the equivalent charge of t
he photon in a plasma.