A waveguide configured for use with a near-eye display (NED) device can include a light-transmissive substrate configured to propagate light rays through total internal reflection and a diffractive optical element (DOE) on a surface of the substrate that is configured to input and/or output light rays to and/or from the substrate. According to some embodiments the DOE can include a diffraction grating made of first material having a first refractive index and a coating of a second material over the diffraction grating, the second material having a second refractive index that is not equal to the first refractive index.