Patent ID: 7379241

Claim:
An apparatus for processing electromagnetic radiation, comprising: a substrate; a plurality of ridges each having a top surface, said ridges being disposed on the substrate and a plurality of grooves disposed intermediate adjacent ridges to form a diffraction grating, each of said ridges comprising a first dielectric material disposed on the substrate having a first index of refraction, and a second dielectric material having a second index of refraction different than the first index of refraction disposed on the first dielectric material; and an overcoat layer having a planar surface that is coplanar with the top surfaces of said ridges; wherein the diffraction grating is constructed and ananged such that the zeroth diffraction orders of a TM-polarized portion and a TE-polarized portion of the electromagnetic radiation are substantially canceled by destructive interference for an angle of incidence of the radiation on the diffraction grating.