  We study experimentally and theoretically the influence of light polarization
on the interference patterns behind a diffracting grating. Different states of
polarization and configurations are been considered. The experiments are
analyzed in terms of electromagnetic energy (EME) flow lines, which can be
eventually identified with the paths followed by photons. This gives rise to a
novel trajectory interpretation of the Arago-Fresnel laws for polarized light,
which we compare with interpretations based on the concept of "which-way" (or
"which-slit") information.
