Propagation of light in a gravitational background

We study the propagation of an electromagnetic field in a weak gravitational background generated by a rotating mass. The solution of the Maxwell equations beyond the geometrical optics shows, together with the well-known deflection and rotation of the polarization plane already present in the geometrical optics approximation, new classical dispersive effects. We analyze such effects at first order in the gravitational constant $G$. In the case of an incoming wave with linear polarization they consist in the development of a component of circular polarization, a breaking of the orthogonality of the electric and magnetic fields, and additional contributions to the deflection of the beam and the rotation of the polarization plane.