Diffractive, waveguide-based, augmented-reality displays couple light from a light engine into an optical waveguide while enabling environmental light to enter the eye. Phase discontinuities at diffraction-grating boundaries of the waveguide can cause a drop in image quality. This disclosure describes techniques to mitigate phase discontinuities between adjacent regions of a grating structure by adjusting the difference in residual layer thickness (RLT) of the waveguide between its blank regions and its input coupler. The RLT can be adjusted by controlling the spacing/size of inkjetted droplets in an inkjet nanoimprint lithography process; by secondary etching/ablation/polishing of the RLT; by introducing a depth offset between the grating and non-grating regions; etc. Phase compensation can be achieved by spatially varying the refractive index of the resin over non-grating regions in an inkjet process; by multi-step inkjet deposition; by depositing dielectric material on the waveguide, etc. A smoothened phase profile results in sharper images, reduced reflections, reduced water-vapor condensation, etc.

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Creative Commons License
This work is licensed under a Creative Commons Attribution 4.0 License.