  A laser interferometric detector of gravitational waves is studied and a
complete solution (to first order in the metric perturbation) of the coupled
Einstein-Maxwell equations with appropriate boundary conditions for the light
beams is determined. The phase shift, the light deflection and the rotation of
the polarization axis induced by gravitational waves are computed. The results
are compared with previous literature, and are shown to hold also for detectors
which are large in comparison with the gravitational wavelength.
