  When an electromagnetic wave is obliquely incident on the interface between
two homogeneous media with different refractive indices, the requirement of
phase continuity across the interface generally leads to a shift in the
trajectory of the wave. When a linearly position dependent phase shift is
imposed at the interface, the resulting refraction may be described using a
generalized version of Snell's law. In this Letter, we establish a formal
equivalence between generalized refraction and blazed diffraction gratings,
further discussing the relative merits of the two approaches.
