To increase the field of view and/or the wavelengths of light (i.e., color bandwidth) transmitted by a waveguide without using high-index resin, some embodiments include a waveguide grating formed on a substrate that is imprinted with a relatively low-index resin and a conformal coating having a relatively high refractive index. In some embodiments, the substrate is imprinted with the resin using nano imprint lithography and the residual layer thickness of the resin layer is minimized. The conformal coating conforms to the geometry of the surface it coats with a substantially uniform thickness.