  We discuss pair creation in a strong laser background. Using lightfront field
theory, we show that all the physics is contained in the lightfront momentum
transfer from the laser, and probe, to the produced pair. The dependence of
this momentum transfer on the geometry of the laser leads to resonance and
diffraction effects in pair production spectra. The lightfront approach
naturally explains the interpretation of laser-stimulated pair production as a
multi-photon process creating pairs of an effective mass.
