Abstract: A waveguide for use in an augmented reality or virtual reality display comprises a plurality of optical structures in or on a photonic crystal. The plurality of optical structures are arranged in an array to provide two diffractive optical elements overlaid on one another in the waveguide. Each of the two diffractive optical elements is configured to receive light from an input direction and couple it towards the other diffractive optical element which can then act as an output diffractive optical element, providing outcoupled orders towards a viewer. The plurality of optical structures have different respective cross sectional shapes, for a cross section parallel to the plane of the waveguide, at different positions in the array in order to provide different diffraction efficiencies at different positions in the array.

Abstract: An optical waveguide combiner includes an optical waveguide substrate and an optical input region. The optical input region includes an optical input diffractive grating integrated in, or disposed on, the optical waveguide substrate. An optical output region includes an optical output diffractive grating integrated in, or disposed on, the optical waveguide substrate, At least one non-diffractive region includes at least one optical non-diffractive array of nanostructures, wherein said at least one optical non-diffractive array of nanostructures is integrated in, or disposed on, the object side of said optical waveguide substrate and at least partially surrounds at least said optical output grating; wherein the external visible reflectance of said at least one non-diffractive array of nanostructures is substantially equal to the external visible reflectance of said optical output grating.