Abstract: An optical waveguide that performs both in-coupling and out-coupling of projected light is provided. The out-coupling region of the waveguide comprises a single-sided or double-sided diffraction grating with at least one of the grating structures conformally coated with a high refractive index material. To reduce the unwanted reflection of light on the waveguide surfaces coated with the high refractive index material, additional antireflective coatings are applied to the diffraction grating areas with the high refractive index coating. The additional antireflective coatings may be very thin to avoid in-coupling, and therefore avoid interference in one or more light rays propagating in the optical waveguide. Alternatively, the antireflective coatings may be very thick to promote in-coupling such that the resulting interference becomes consistent across all light rays propagating in the optical waveguide.