  Photon propagator for power-law inflation is considered in the general
covariant gauges within the canonical quantization formalism. Photon mode
functions in covariant gauges are considerably more complicated than their
scalar counterparts, except for the special choice of the gauge-fixing
parameter we call the simple covariant gauge. We explicitly construct the
position space photon propagator in the simple covariant gauge, and find the
result considerably more complicated than its scalar counterpart. This is
because of the need for explicitly inverting the Laplace operator acting on the
scalar propagator, which results in Appell's fourth function. Our propagator
correctly reproduces the de Sitter and flat space limits. We use this
propagator to compute two simple observables: the off-coincident field
strength-field strength correlator and the energy-momentum tensor, both of
which yield consistent results. As a spinoff of our computation we also give
the exact expression for the Coulomb gauge propagator in power-law inflation in
arbitrary dimensions.
